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QNP2022 - The 9th International Conference on Quarks and Nuclear Physics
The 9th International Conference on Quarks and Nuclear Physics will be fully online and hosted by Florida State University on 5-9 September, 2022. This conference follows the series of meetings previously held in Adelaide, Julich, Bloomington, Madrid, Beijing, Palaiseau, Valparaiso, and Tsukuba.
Experimenters and theorists discuss recent developments in the field of hadron and nuclear physics, continuing previous discussions and presenting new results on the quark and gluon structure of hadrons, hadron spectroscopy and decays, hadron interactions and nuclear structure, and hot and cold dense matter.
The talk will review information gained on the phase diagram of strongly
interacting matter from low to high net baryon densities. It will cover
the liquid gas phase transition and focus on the chiral phase transition
and deconfinement at high temperature. At the LHC experimental data point
to the formation on deconfined matter in a net-baryon free hot fireball,
conditions as encountered in the first microseconds of the early universe.
The purpose of COMPASS is the study of hadron structure
and hadron spectroscopy with high intensity muon and hadron beams.
The Collaboration is formed by about 200 physicists from 25 countries.
The facility was approved 25 years ago and the physics experiments
started in 2002 with a muon beam, polarised proton and deuteron
targets. These semi-inclusive deep inelastic scattering (SIDIS)
reveals a detailed quark-gluon structure of the nucleon, in particular
the gluon polarisation and transverse-momentum-dependent correlations.
The years 2008 and 2009 were dedicated to the hadron spectroscopy
programme with pion and proton beams scattering off a liquid
hydrogen target and nuclear targets. An unprecedented amount
of data was collected and showed subtle details
of the light-meson spectrum. A dedicated study of the pion
polarisability using Primakoff scattering of pions from heavy nuclei
was also performed.
Phase II of COMPASS commenced in 2014 and is primarily devoted to
the transverse and 3D structure of nucleons using Deeply Virtual
Compton scattering (DVCS), Hard Exclusive Meson Production (HEMP),
SIDIS and polarised Drell-Yan (DY) reactions.
A panorama of the recent COMPASS results will be presented.
The study of baryonic excited states provides fundamental information on the internal
structure of the nucleon and on the degrees of freedom that are relevant for QCD at low
energies. N* are composite states and are sensitive to details of the how quarks are
confined. Meson photo-and electro-production reactions have provided complementary
information on light quark baryon spectroscopy for several decades, but a crucial step
forward has been the advent of large solid angle detectors, together with polarized
beam and targets, which gave access to single and double polarization observables. The
Q 2 dependence of excited baryons electro-couplings has also been measured, gaining
insight into the internal structure of baryons.
The CLAS12 energy upgrade opened an “exciting” new era in baryon spectroscopy,
including the search for hybrid hadrons, in which gluons appear as constituent
components beyond the valence quarks.
Streaming Readout has been adopted as the paradigm of data acquisition (DAQ) at many major experiments at LHC, RHIC, and the future EIC. Distinct from the traditional triggered readout, streaming DAQs rely on modern digital data processing for large factors of data reduction, which opens unique opportunities for the application of AI/ML that is high throughput, low latency, energy efficient, and reliable. In this talk, we will discuss an array of AI/ML applications for Streaming Readout on the platforms of ASICs, FPGAs, and novel AI accelerators.
I review recent developments in the application of machine learning techniques to problems in nuclear theory, with a particular emphasis on generative models for lattice quantum field theory.
Exclusive reactions measured at the intensity frontier open new opportunities to study QCD. Processes in a multi-dimensional phase space require adequate tools to take advantage of correlations between variables that embed the underlying strong-force interaction. To extend our capability of interpreting multi-dimensional data and fully reconstruct correlations between final state particles, we propose a new approach that uses AI-based algorithms trained on real data to unfold detector effects and reveal the interaction mechanisms at the vertex level. The A(i)DAPT project is a collaborative effort between experimental and theoretical physicists and data scientists to develop new methods of extracting the underlying physics with state-of-the-art machine learning techniques, such as generative adversarial networks. In this contribution, I will present the project and some selected results obtained in inclusive and exclusive electron and photon scattering from protons.
Jefferson Laboratory (JLab) is home to the Continuous Electron Beam Accelerator Facility (CEBAF) and four experimental physics halls. JLab’s data science portfolio includes projects to advance research in nuclear physics, accelerator facilities, and engineering. With a specific focus on expanding capabilities in machine learning (ML)-based uncertainty quantification, design and control, and developing interpretability techniques. Examples of ML being used in JLab’s experimental halls and in collaborations with Oak Ridge National Lab (ORNL) and Fermilab will be shown. From JLab, an example of a production application using ML in an experimental hall resulting in 35% improvement in physics statistics due to significant improvement in track reconstruction efficiency, as well as an example of online detector calibration through high voltage control that is expected to decrease computation time when compared to traditional methods. Two applications developed in collaboration with JLab will be presented that implement uncertainty quantification using the new Deep Gaussian Process Approximation method: anomaly detection for the Spallation Neutron Source accelerator at ORNL, and a surrogate model for booster control at Fermilab.
Artificial Intelligence (AI) for design is a relatively new but active area of research but when it comes to detector design, surprisingly this is an area of applications at its infancy.
Nonetheless the Electron Ion Collider (EIC), the future ultimate machine to study the strong force, utilized AI starting from the design phase. EIC is a large-scale experiment with an integrated detector that covers the central, far-forward, and far-backward regions. In general, we deal with compute intensive simulation and detectors made by multiple sub-detectors, each characterized by a multidimensional design space and multiple design criteria. In this context, AI offers state of the art solutions to design detectors in an efficient way. This talk provides an overview of these techniques and recent progress made during the EIC detector proposal; it will also cover how this work could further progress in the near future.
Recent results of coupled channel partial wave analyses with various $\bar{p}p$-annihilation, $\pi\pi$- and $\pi^-p$-scattering data performed with the powerful and user-friendly PAWIAN (Partial Wave Interactive Analysis) package will be presented. By considering analyticity and unitarity conditions using the K-matrix approach with Chew-Mandelstam functions, pole positions and decay branching fractions for numerous light mesons could be determined. Also a significant contribution of the $\pi_1$-wave has been identified in $\bar{p}p$ in-flight data from Crystal Barrel. In particular the coupling of the amplitudes identified in the $\bar{p}p$ channels with the $\pi_1$- and $a_2$-waves seen in the $\pi^- p$-process measured at COMPASS could provide new insights for a better understanding of this spin exotic $I^G(J^{PC})=1^-(1^{-+})$ wave in the mass region below 2 GeV$/c^2$.
The primary goal of the GlueX experiment at Jefferson Lab is to search for and map the spectrum of light hybrid mesons. Many experiments have studied and reported evidence of exotic mesons decaying into $\eta\pi$ and $\eta'\pi$ final states. GlueX, which has a linearly polarized photon beam and a large acceptance for both charged and neutral particles, has access to both the neutral, $\gamma p\to\eta\pi^{0}p$, and charged, $\gamma p\to\eta\pi^{-}\Delta^{++}$, processes. This presentation will discuss the amplitude analysis of $a_2\to\eta\pi$ channels at GlueX. It will focus on and compare the extraction of differrential cross sections for $a_{2}\to\eta\pi$ as a function of $t$ for both the neutral and charged processes. This work is the first step towards studying the production of the hybrid $\pi_{1}(1600)$ in $\eta(')\pi$ channels at GlueX.
We calculate, from Lattice QCD, the elastic $\pi \pi$ scattering amplitude in the isoscalar $I=0$ channel, and determine the $\sigma$ estate. We extract its lineshape for two different quark masses corresponding with $m_\pi \sim 330$ and $283$ MeV; where it is predicted that this state transitions from bound to virtual bound. In order to provide an accurate picture we use a high statistics volume for the heavier pion mass, and two for the lighter. The comparison between the two masses showcases very different lineshapes for the phase shifts. This is related to the different behavior of the $\sigma$ for these values of its quark mass dependence.
We present a first calculation of the $K\gamma \to K\pi$ transition amplitude in the presence of a resonant $K^*$ from lattice quantum chromodynamics. In this process, the kaon interacts with a photon and scatters strongly to a $K\pi$ in the final state. The $K\pi$ state is in a lowest relative $S$ $\&$ $P$-wave, with the $K^*$ resonance appearing in the $P$-wave.
The matrix elements for the $K\gamma \to K\pi$ transition are calculated in finite-volume lattice QCD. To map these matrix elements to the infinite volume transition amplitudes which are measured in experiments, we apply the Lellouch-Lüscher formalism. We determine the transition amplitude for different $K\pi$ energies and photon virtualities to observe an enhancement due to the $K^*$ resonance. From the energy dependence, we extract the $Kγ \to Kπ$ transition form factor for the unstable $K^*$ by analytically continuing into the complex energy plane and calculating the residue at the $K^*$ pole.
Using the world’s largest samples of J/psi and psi(3686) events produced in e+e- annihilation, BESIII is uniquely positioned to study light hadrons in radiative and hadronic charmonium decays. In particular, exotic hadron candidates including multiquark states, hybrid mesons and glueballs can be studied in high detail. Recent highlights from the light hadron spectroscopy program, including the observation of an iso-scalar spin-exotic 1-+ state η1(1855) in J/ψ→γηη′, the observation of X(2600) in J/ψ→γπ+π-η′ and a partial wave analysis of the decay J/ψ→γη′η′, will be presented.
The quark-gluon dynamics manifests itself in a set of non-perturbative functions describing all possible spin-spin and spin-orbit correlations. Single and Dihadron semi-inclusive and hard exclusive production, both in current and target fragmentation regions, provide a variety of spin and azimuthal angle dependent observables, sensitive to the dynamics of quark-gluon interactions. Studies of evolution properties of observables in SIDIS, and validation of the existing theory, is a challenging task, which will require high precision measurements in multidimensional bins.
In this talk, we present an overview of the current status and some planned measurements of the orbital structure of nucleons at JLab, and possible extensions to future physics program of upgraded to 20-24 GeV JLab .
Exclusive scattering processes as deeply virtual Compton scattering (DVCS) are very promising tools to study the three-dimensional partonic structure of any hadronic system from a new point of view. With respect to the collinear information obtained in deep inelastic scattering experiments, complementary and richer information about the innermost constituents can be achieved. As a matter of fact, the structure functions that can be accessed in DVCS are the generalized parton distributions (GPDs), non-perturbative objects encoding the correlation between the spatial and the momentum degrees of freedom of the constituent partons.
Moreover, considering nuclei as targets, two channels, the one where the initial nucleus breaks up after the scattering and the one where a bound nucleon can be detected in the final state after the breaking up, can be analyzed. The information that can be obtained in this way can be used also to dig more into longstanding open questions like the origin of the EMC effect, i.e. the modification of the bound nucleons’ parton structure induced by the nuclear medium.
In this talk, we will present phenomenological models able to describe the hadronic structure of nuclei within the GPD framework. In order to properly account for the nuclear effects entering the description of such reaction mechanisms, a realistic solution of the Schrödinger equation is needed in order to have a realistic description of the nuclear environment.
Light nuclei are paradigmatic systems for these studies since realistic nucleon-nucleon potential including three-body forces can be taken into account in the calculation.
While for $^4$He, the numerical results of our approach have already a well established comparison with the Jefferson Lab experimental data (for both the channels), preliminary results for a DVCS process off a neutron/proton bound in $^2$H will be shown.
Eventually, after a detailed description of our theoretical approaches, a glimpse on the phenomenology that can be done with these models in view of the EIC will be caught.
It is often taken for granted that Generalized Parton Distributions (GPDs) are defined in the "symmetric" frame, where the transferred momentum is symmetrically distributed between the incoming/outgoing hadrons. However, such frames pose more computational challenges for the lattice QCD practitioners. In this talk, we lay the foundation for lattice QCD calculations of GPDs in non-symmetric frames, where the transferred momentum is not symmetrically distributed between the incoming/outgoing hadrons. The novelty of our approach relies on the parameterization of the matrix elements in terms of Lorentz-invariant amplitudes, which helps in not only isolating but also reducing part of the higher-twist contaminations as a byproduct. This work opens possibilities for faster and more effective computations of GPDs.
In this talk I will revisit the evolution of generalised parton distributions (GPDs) in momentum space.
I will present a recalculation of the evolution kernels in the MSbar scheme at one-loop accuracy, confirming previous results.
The kernels are arranged in a form suitable for numerical implementation allowing for an easy implementation in an existing open source code (APFEL++).
I will then scrutinise the properties of these kernels and their effect on the evolution of GPDs.
Specifically, I will obtain general conditions on the evolution kernels deriving from the GPD sum rules, showing that our formulation obeys these conditions.
I will then show analytically that our calculation reproduces the DGLAP and the ERBL equations in the appropriate limits and that it guarantees the continuity of GPDs.
I will then move to show that our numerical implementation of GPD evolution fulfils DGLAP and ERBL limits, continuity, and polynomiality.
Finally, I will benchmark the numerical implementation against analytical evolution in conformal space and against an existing implementation of GPD evolution.
Generalized Parton Distributions (GPDs) are nowadays the object of an intense effort of research,
in the perspective of understanding nucleon structure. They describe the correlations between
the longitudinal momentum and the transverse spatial position of the partons inside the nucleon
and they can give access to the contribution of the orbital momentum of the quarks to the nucleon
spin.
Deeply Virtual Compton scattering (DVCS), the electroproduction on the nucleon, at the quark
level, of a real photon, is the process more directly interpretable in terms of GPDs of the nucleon.
Depending on the target nucleon (proton or neutron) and on the DVCS observable extracted
(cross sections, target- or beam-spin asymmetries, ...), different sensitivity to the various GPDs
for each quark flavor can be exploited. GPDs can also be accessed in other reactions, such as
Timelike Compton Scattering, Double DVCS, or the exclusive electroproduction of mesons.
This talk will provide an overview on recent and new, promising, GPD-related experimental
results, mainly obtained at Jefferson Lab with a 12-GeV electron beam, for various target types
and final states. These data open the way to a “tomographic” representation of the structure of
the nucleon, allowing the extraction of transverse space densities of the quarks at fixed
longitudinal momentum, as well as providing an insight on the distribution of forces inside the
nucleon.
The perspectives for future JLab experiments using a polarized positrons beam will also be
outlined.
Since the properties of the initial state of heavy-ion collisions are not directly accessible in experiments, there currently exists a variety of different models employed in fluid dynamic simulations of heavy-ion collisions.
In this talk I will give a brief overview over different initial-state models and introduce a new method to characterize initial density profiles by decomposing them in terms of an average state and an orthonormal basis of modes that represent the event-by-event fluctuations of the initial state.
The basis is determined such that the probability distributions of the amplitudes of different modes are uncorrelated.
Based on this decomposition, the different types and probabilities of event-by-event fluctuations in Glauber and Saturation models can be quantified and it is possible to investigate how the modes affect the characteristics of the initial state.
Simulations of the dynamical evolution in K{\o}MP{\o}ST and MUSIC show the impact of the various modes on final-state observables and their correlations.
Ultra-relativistic heavy-ion collisions are expected to produce some of the strongest magnetic fields ($10^{13}$ $-$ $10^{16}$ Tesla) in the Universe. The initial strong electromagnetic fields have been proposed as a source of linearly-polarized, quasi-real photons that can interact via the Breit-Wheeler process to produce $e^{+}e^{-}$ pairs.
In this talk, we will present latest STAR measurements of $e^{+}e^{-}$ pair production in ultra-peripheral and peripheral Au+Au collisions at $\sqrt{s_{NN}} =$ 200 GeV. A comprehensive study of the pair kinematics is presented to distinguish the $\gamma\gamma\rightarrow e^{+}e^{-}$ process from other possible production mechanisms. Furthermore, we will present and discuss the observation of a 4th-order azimuthal modulation of $e^{+}e^{-}$ pairs produced in the Breit-Wheeler process. The striking 4th-order angular modulation is a direct result of vacuum birefringence, a phenomenon predicted in 1936 that empty space can split light according to its polarization components when subjected to a strong magnetic field. Their implications for the properties of the magnetic filed produced in heavy-ion collisions will be discussed.
The primary goal of the ultrarelativistic heavy-ion collision program at the LHC is to study the quark-gluon plasma (QGP) properties, a state of strongly interacting matter that exists at high temperatures and energy densities. However, the lack of knowledge on the initial conditions of heavy-ion collision results in significant uncertainty in the extraction of the transport properties of QGP.
In this talk, I will present the latest developments in multi-particle correlations. I will show that the newly proposed mixed harmonic correlation of various moments of anisotropic flow coefficients can provide strong constraints on the correlations between various moments of eccentricity coefficients in the initial conditions. Both hydrodynamic model predictions and ALICE measurements will be discussed. In addition, I will discuss the most recent studies on the correlation between mean transverse momentum and anisotropic flow coefficients, which could reflect the size and shape of the initial state and give direct access to the initial conditions. I will present the latest experimental measurements from the LHC experiments and several recent theoretical model predictions. In particular, I will highlight the current discrepancies between the experimental data and the state-of-the-art understanding of the initial conditions extracted from the Bayesian analyses. In the end, I will discuss potential improvements in the descriptions of initial conditions.
The Quark–Meson–Coupling (QMC) model self-consistently relates the dynamics of the internal quark structure of a hadron to the relativistic mean fields arising in nuclear matter. The QMC energy density functional (EDF) was successfully employed to investigate several ground state properties of even-even finite nuclei across the nuclear chart. In this presentation, the latest developments in the QMC EDF which includes higher-order density dependence as well as tensor and pairing interactions, will be discussed. Most importantly, predictions of the QMC model for several nuclear observables for all even-even finite nuclei will be presented. Such predictions were found to be comparable with results from other nuclear models despite having significantly fewer number of the QMC model parameters.
Systems of few interacting neutrons have long fascinated nuclear physicists,
with ample of theoretical and experimental activity throughout the decades.
Interest in these systems has recently surged in light of new indications that
few-body resonances comprised of neutrons may exist in nature. In this talk, I
will present studies of few-neutron systems based on pionless effective field
theory, which provides the most general description of the neutron-neutron
interaction at low energies.
A realistic description of atomic nuclei, in particular light nuclei characterized by clustering and low-lying breakup thresholds, requires a proper treatment of continuum effects. We have developed an approach, the No-Core Shell Model with Continuum (NCSMC) [1,2], capable of describing both bound and unbound states in light nuclei in a unified way. With chiral two- and three-nucleon interactions as the only input, we can predict structure and dynamics of light nuclei and, by comparing to available experimental data, test the quality of chiral nuclear forces.
We will discuss applications of NCSMC to the proton emission in 11Be β decay [3], the 2H+α [4], the p+7Be [5], and p+7Li radiative capture and the production of the hypothetical X17 boson claimed in ATOMKI experiments [6]. The 7Be(p,γ)8B reaction plays a role in Solar nucleosynthesis and Solar neutrino physics and has been subject of numerous experimental investigations while the 2H(α,γ)6Li is responsible for the 6Li production in the Big Bang. The proton emission in 11Be β decay was observed in a recent TRIUMF experiment and disproves a hypothetical neutron decay to a dark matter particle [7].
Supported by the NSERC Grants No. SAPIN-2016-00033 and SAPIN-2022-00019 and by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Work Proposals No. SCW1158 and No. SCW0498. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. This work was prepared in part by LLNL under Contract No. DE-AC52-07NA27344. Computing support came from an INCITE Award on the Summit supercomputer of the Oak Ridge Leadership Computing Facility (OLCF) at ORNL, from the Digital Research Alliance of Canada, and from the LLNL institutional Computing Grand Challenge Program.
[1] S. Baroni, P. Navratil, and S. Quaglioni, Phys. Rev. Lett. 110, 022505 (2013); Phys. Rev. C 87, 034326 (2013).
[2] P. Navratil, S. Quaglioni, G. Hupin, C. Romero-Redondo, A. Calci, Physica Scripta 91, 053002 (2016).
[3] M. C. Atkinson, P. Navratil, G. Hupin, K. Kravvaris, S. Quaglioni, Phys. Rev. C 105, 054316 (2022).
[4] K. Kravvaris, P. Navratil, S. Quaglioni, C. Hebborn, G. Hupin, arXiv: 2202.11759.
[5] C. Hebborn, G. Hupin, K. Kravvaris, S. Quaglioni, P. Navratil, P. Gysbers, Phys. Rev. Lett. 129, 042503 (2022).
[6] A. J. Krasznahorkay et al., Phys. Rev. Lett. 116, 042501 (2016).
[7] Y. Ayyad et al., Phys. Rev. Lett. 123, 082501 (2019).
We demonstrate that paradigm shift from considering deuteron as a system of bound proton
and neutron to considering it as a pseudo-vector system in which we observe proton and neutron, results in a possibility of probing a new "incomplete" P-state structure on the light-front (LF), at extremely large internal momenta, which can be achieved at high energy transfer electro-disintegration of the deuteron.
Investigating the deuteron on the light-front, where the vacuum-fluctuations are suppressed, we found that this new structure, together with conventional
S- and D- states, is a leading order in transferred energy of the reaction, thus it is not suppressed on the light-front.The incompleteness of the observed P-state results in a violation of angular condition which can happen only if deuteron contains non-nucleonic structures such as $\Delta$-$\Delta$, $N^*N$ or hidden color components. We demonstrate that experimentally verifiable signatures of ``incomplete" P-states are transverse momentum dependence of
LF momentum distribution of the nucleon in the deuteron as well as an enhancement of the tensor polarization strength beyond the S- and D- wave predictions at large internal momenta in the deuteron.
First proposed by Nobel laureate Weinberg in the early 1990s, the so-called Weinberg chiral nuclear force has become the de facto standard for ab initio nuclear structure and reaction studies. However, unlike atomic physics and chemistry, the application of relativistic ab initio methods in nuclear physics is just emerging. An important factor hindering their development is the lack of modern relativistic nucleon-nucleon interactions. To provide the most wanted inputs for relativistic nuclear structure and reaction studies and to better understand the non-perturbative strong interaction, we proposed the construction of a relativistic chiral nuclear force in 2016[1,2]. After many years of extensive studies [3,4,5,6], we have obtained the first high-precision relativistic chiral nuclear force [7]. This talk will introduce its main features and discuss about its future applications and further development.
References
[1] X.L. Ren, K.W. Li, L.S. Geng, B.W. Long, P. Ring and J. Meng, Chin. Phys. C 42, 014103(2018).
[2] K.W. Li, X.L. Ren, L.S. Geng and B.W. Long, Chin. Phys. C 42, 014105 (2018).
[3] Y. Xiao, L.S. Geng and X.L. Ren, Phys. Rev. C 99, 024004(2019).
[4] J.X. Lu, L.S. Geng, X.L. Ren and M.L. Du, Phys. Rev. D 99, 054024(2019).
[5] Y. Xiao, C.X. Wang, J.X. Lu and L.S. Geng, Phys. Rev. C 102, 054001(2020).
[6] C.X. Wang, J.X. Lu, Y. Xiao and L.S. Geng, Phys. Rev. C 105, 014003(2022).
[7] J.X. Lu, C.X. Wang, Y. Xiao, L.S. Geng, J. Meng and P. Ring, Phys. Rev. Lett. 128, 142002(2022).
Exact solutions for energy eigenvalues and eigenstates for transitional nuclei in the spd-interacting boson model are found by using an infinite dimensional algebraic method. It has been shown that the spd-IBA is a quite powerful model for analyzing nuclear structures. In this lecture, we have studied the GDRs within an extended pairing model with a focus on spectral statistics. The effect of pairing correlations on spectral statistics is the primary result of this lecture. We have found that varying the pairing interaction strength for vector boson is likely to modify the statistical properties of the spectra. We report on a study of the spectral statistics associated with dipole resonances in medium mass nuclei. Calculated energy spectra around the critical point of the vibrational to γ -soft transitions emerge to approach those of a Gaussian orthogonal ensemble, while near the rotational and vibrational limits of the theory, the spectra exhibit a more regular pattern. By changing the weights of the pairing terms in Hamiltonian, results are obtained that show more regular‑like statistics over the critical point area. Because of the reasonable success of the giant dipole resonance in chaos and regularity of nuclei, the investigation of another extension of the interacting boson model in sdf-, sdg-, and spdf-boson systems should be possible.
Significant progress has been realized in studies of excited nucleon state structure (N program) from the data on exclusive meson electroproduction measured with the CLAS detector in Hall B at Jefferson Laboratory (JLab). Studies of N program give us the unique opportunity to explore the complex interplay of quark-gluon and meson-baryon degrees of freedom in the N structure and the transition from quark-gluon confinement towards perturbative QCD as it is revealed in the structure of excited nucleons with different quantum numbers. New high statistics experimental data with the CLAS12 detector following 12 GeV upgrade have been taken to extract the N electrocouplings at high photon vitalities (Q2) ever achieved up to 10-12 GeV2. This high-Q2 reach will shed light on the transition between the cloud of hadrons and the core of three confined quarks in N structure. This talk will review the current status of N program with CLAS and discuss on-going efforts with CLAS12.
Recently structures in invariant mass distributions and excitation energy spectra have been attributed to triangular singularities as discussed in e.g., [1, 2] and in the review by Guo et al.[3]. These singularities emerge under specific kinematic conditions when new reaction channels open up. It will be shown that a triangular singularity associated with the opening of the γp → pa0 → pπ0η channel can explain the observation of a structure in the Mpη invariant mass distribution near 1700 MeV/c2 in the γp → pπ0η reaction [4]
References
[1] G. D. Alexeev et al., The COMPASS Collaboration, Phys. Rev. Lett 127, 082501 (2021).
[2] M. Mikhasenko, B. Ketzer and A. Sarantsev, Phys. Rev. D 91, 094015 (2015).
[3] F. K. Guo et al., Rev. Mod. Phys. D 90, 015004 (2018).
[4] V. Metag et al.,EPJA 57, 325 (2021).
∗Supported by DFG through SFB/TR16.
The new results from the Bonn-Gatchina partial wave analysis are presented. The new solution includes the new data on the meson production off the neutron and the data on the omega-meson photoproduction. The spectrum and properties of the observed baryons are discussed.
The dynamics of photoproduced baryonic systems has lacked clear understanding, due to the absence of both precise data and of theoretical attention. Using data collected in Hall D of the Thomas Jefferson National Accelerator Facility, we have for the first time studied the reaction mechanisms of the photoproduced baryon-antibaryon pairs $\gamma p \to \mathcal{\overline{B}B}$$p$, where $\mathcal{\overline{B}B}$ includes $\overline{p}p$ and $\overline{\Lambda}\Lambda$ (with $\Lambda \to \pi^- p, \overline{\Lambda} \to \pi^+ \overline{p}$) with photon beam energy from reaction thresholds up to 11.4 GeV. Several distinct reaction mechanisms producing $p\bar{p}$, $\Lambda\bar{\Lambda}$ and $p\bar{\Lambda}$ systems have been identified using realistic Monte Carlo models that were matched to the measured kinematic observables seen in the experiments. The interactions in these baryonic systems were studied using (so far preliminary) differential cross-sections, invariant mass, and three-body angular correlation measurements. Preliminary total cross-sections of different reactions will also be compared. In addition, preliminary measurement of hyperon polarization, spin correlation, and beam asymmetries extracted from the GlueX photon energy range between 8.2 and 8.8 GeV will be presented.
The FROST experiment at Jefferson Lab used the CLAS detector in Hall B with the intention of performing a complete and over-determined measurement of the polarization observables associated with strangeness photoproduction, in combination with data from previous JLab experiments as part of the N* program. This was achieved by utilizing the FROST polarized target in conjunction with polarized photon beams, allowing direct measurement of beam-target double polarization observables.
Although sufficient observables have now been measured to enable the associated reaction amplitudes to be determined, facilitating a near model-independent partial wave analysis, global data in strangeness channels is a couple of orders of magnitude smaller than pion photoproduction, so some ambiguities remain. These can be resolved by measuring observables spanning combinations of beam, target and recoil polarization. Furthermore, the recent revision to the value of the weak decay parameter makes a wider range of observable measurements even more desirable as a cross-check of interpretations of previous data. Studies on strangeness photoproduction reactions may provide evidence of previously undetermined resonances, due to the different coupling strengths of these states to other reaction channels.
The G polarization observable is one of the beam-target double polarization observables, associated with a longitudinally polarized target and a linearly polarized photon beam, and its measurement for the strangeness reaction $\gamma p \rightarrow K^{+}\Lambda$ is the focus of the work presented.
We present the most recent extraction of unpolarized transverse-momentum-dependent (TMD) parton distribution functions (PDFs) and TMD fragmentation functions (FFs) from global data sets of Semi-Inclusive Deep-Inelastic Scattering (SIDIS), Drell-Yan and Z boson production. The fit is performed at the N$^3$LL logarithmic accuracy in the resummation of q$_T$-logarithms and features flexible non-perturbative functions, which allow to reach a very good agreement between theory and the experimental data. In particular, we address the tension between the low-energy SIDIS data and the theory predictions.
The transverse momentum dependent and collinear factorization theorems are independent approaches to the description of scattering cross-sections at high energy. They operate with different set of universal distributions, namely, the transverse momentum distributions (TMDs) and collinear distributions. However, these distributions are not entire independent. In the regime of large transverse momentum or small-$b$ (where $b$ is a Fourier conjugated parameter to the transverse momentum), TMDs can be factorized in the terms of collinear distributions. This relation is often refereed as ``matching relation'', and is a consequence of operator product expansion. In this talk, I will present the small-b expansion for the Sivers, Boer-Mulders, worm-gear-T and worm-gear-L functions, up to next-to-leading order (NLO).
The majority of TMDs match the collinear distributions at higher twists. For that reason their consideration is cumbersome.
The usage of the matching relation is very important for the phenomenology. It allows to incorporate the already known functions into TMDs, and in this way, reduces the parametric freedom of TMD.
Semi-Inclusive Deep Inelastic Scattering on nuclei offers a new way to gain microscopic information about the mechanisms of parton propagation and hadron formation in QCD. The interactions with the nuclear medium of the partonic and hadronic participants in the hadronization process can reveal features of that process at the femtometer distance scale. New data from CLAS on baryon hadronization in nuclei for the lambda baryon and for the proton may offer the potential of understanding more about the role of diquark correlations as a feature of nucleon structure, and more generally the in-medium interaction of colored qq pairs in the final state. Comparisons of the new data to the predictions of the GiBUU model, which generally describes meson production from nuclei quite well, intriguingly suggest that our picture of baryon production from nuclei is incomplete.
The thrust distribution associated with single-inclusive $e^+e^-$ annihilation (SIA$^{\text{thr}}$), sensitive to the transverse momentum of the detected hadron with respect to the thrust axis, represents one of the most challenging and promising case where to extend the TMD factorization beyond the standard processes. At present days, its factorization properties have been studied through two different approaches, based on SCET framework and CSS formalism respectively.
Oddly, the two approaches show some tension in the results associated with the kinematic region in the bulk of the phase space, while they agree at its boundaries.
Clarifying the origin of such differences is one of the main aims of this talk. In particular, I will point out how the discrepancies are due to non-perturbative effects, so that the perturbative QCD alone leads blindly to a unique answer. The factorization theorem is then presented at NNLL in thrust and transverse momentum, properly addressing the correlation among these (measured) variables and the rapidity divergences regulator.
In the recent years, it has been realized that deep-inelastic scattering with polarization control could provide a variety of spin and azimuthal angle dependent observables sensitive to the quark-gluon interactions. New parton distributions and fragmentation functions have been introduced to describe the rich complexity of the hadron structure and move towards a multi-dimensional imaging of the underlying parton correlations. Besides the hard probe scale, these functions explicitly depend on the parton transverse degrees of freedom at the scale of confinement. Their study promises to open a unprecedented gateway to the peculiar nature of the strongly interacting force.
This work presents a selection of available observations and upcoming measurements planned at Jefferson Lab and at the future Electron-Ion Collider to address the mysteries of the nucleon structure from a modern point of view.
The collisions of heavy nuclei at ultra-relativistic LHC energies produce an extreme phase of strongly-interacting matter called the quark-qluon plasma (QGP). Since more than 10 years the ALICE Collaboration at CERN has been studying the nature of the QGP by analysing the data from various collision types provided by the LHC: proton-proton, proton-nucleus and nucleus-nucleus. Here, the results from the first two collision systems both serve as a baseline for the studies of heavy-ion collisions and are interesting in their own right.
In this talk we present some recent ALICE highlights from the harvest of the data collected during the second period of LHC operation (Run 2). Thanks to excellent tracking and particle identification capabilities of the detector, ALICE has significantly contributed not only to our understanding of the properties of strongly-interacting matter under extreme conditions, but also to various fields of physics beyond the studies of the QGP. Finally, a brief outlook on ALICE perspectives in the Run 3 and Run 4 data-taking campaigns will be shown.
Relativistic nuclear collision experiments explore the physics of dense and hot nuclear matter, the so-called quark-gluon plasma (QGP). The bulk properties of such matter can be inferred indirectly from the yields and correlations of the produced hadrons. Nevertheless, the relevant degrees of freedom of the QGP and are subject to the effects of multiple rescatterings and non- perturbative physics of hadronization, as described by Quantum Chromodynamics (QCD), which tend to erase information about the earlier stages of the collision. Electromagnetic probes, e.g., photons and dilepton production, are radiated throughout the evolution of a heavy ion collision (HIC) and, due to a lack of final-state interactions, can escape the medium virtually unscathed. Therefore, measuring their spectra and their correlations gives a unique window virtually to every stage of the evolution of the medium, the so-called fireball. In this talk I will give a brief introduction to such penetrating probes, their main properties and results, as well as the puzzles and challenges ahead.
This talk presents a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive charged particle yields in 13 TeV pp collisions. These correlations, and in particular their comparison between excited and ground state Upsilons meson, lead to surprising conclusions about heavy quarkonium production and hadronization. Measurements of charged particles in events with different Upsilon states are studied in intervals of Upsilon momentum. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV pp data. This measurement benefits from novel application of statistical techniques to remove the combinatorial and pileup backgrounds leading to increased sensitivity. A description of the technical challenges associated with an inclusive hadron analysis in high-pileup pp data will be shown, as well as the results and their physics implications.
Study of the QCD phase diagram is important for understanding the physics of the early universe and the interiors of high-density stars. Recently, experiments such as RHIC or GSI have been conducted to explore a wide range of the phase diagram including the QCD critical point. From theoretical analyses, there are many previous studies using lattice QCD or effective models. However, the full picture of the QCD phase diagram has not yet been clarified. Since quantum fluctuations have a large influence on a system behavior near the QCD critical point, one should use a method to take quantum fluctuations into account, when analyzing the entire phase diagram.
We use the Functional Renormalization Group method (FRG) to analyze the chiral phase transition in terms of the 2-flavor Quark-Meson model. The FRG allows us to include effects of quantum fluctuations in a systematic non-perturbative way. However, because of its non- perturbative effects, the FRG equation is not a closed form. Therefore, the Local Potential Approximation (LPA) is often used as the simplest truncation scheme. The LPA has been suggested to give reasonable results for chiral phase transitions at finite temperature in ref. [1][2]. We consider the scale dependence of the effective potential for the meson field φ, the Yukawa interaction coupling g, the quark and meson wave function renormalizations Zq, Zφ. To solve the flow equation numerically in ref. [1][2], the effective potential U(φ) is assumed to be given a finite Taylor series about scale independent expansion points. However, use of this method is questionable for the study of the first-order phase transition at low temperature and high density, accompanied with a discontinuous change of the chiral order parameter. In our study, we use the grid method to solve the flow equation, in which the field φ is the discretized in a one-dimensional grid. This enables us to access the full φ dependence of the effective potential and to describe the first-order phase transition. As a result, we obtain numerical results for the scale dependence of the chiral order parameter, Z φ, and Zq at zero temperature, which agree with those of [3]. The resulting phase diagram at finite temperature is also consistent with the previous work [1][2]. We further discuss the phase diagram at high density, where the first order chiral phase transition is thought to occur.
[1] Jan. M. Pawlowski and F. Rennecke, “Higher order quark-mesonic scattering processes and the phase structure of QCD”, Phys. Rev. D 96, 076002 (2014)
[2] F. Rennecke and B. -J. Schaefer, “Fluctuation-induced modifications of the chiral phase structure in (2+1)-flavor QCD”, Phys. Rev. D 96, 016009 (2017)
[3] Jü rgen Eser, et al. “Low-energy limit of the O(4) quark-meson model from the functional renormalization group approach”, Phys. Rev. D 98, 014024 (2018)
The exact dynamics of the quarks and gluons inside the nucleon are a long-standing question in hadron physics. To shed more light on this topic, the excitation spectrum of the nucleons needs to be measured and compared to theoretical models like constituent quark models or lattice QCD calculations. Until now, most of the predicted resonances - especially at high masses - have not been found by experiments, which is the well-known missing resonances problem.
The search for the missing resonances is a recent research project by several different experiments. One of them is the CBELSA/TAPS experiment, which is located at the ELSA accelerator in Bonn, Germany. The CBELSA/TAPS experiment features a detector system with nearly full 4π angular coverage and a high detection efficiency for photons, which makes it the ideal tool for the measurement of final states comprising neutral mesons. One of its special features is the use of linearly or circularly polarized photon beams impinging on a longitudinally or transversely polarized butanol target. This allows for the measurement of single or double polarization observables, which are of major importance for the identification of small resonance contributions.
In this talk, an overview of the recent status in baryon spectroscopy at the CBELSA/TAPS
experiment will be given. This includes the measurement of different polarization ob-
servables, as well as a review of the impact of the polarization data on the excitation
spectra of the nucleons.
Recently, the LHCb and BES III experiments have reported several exotic flavor states which cannot be accomodated into $q\bar{q}$ states. Theoretical predictions of some of these states were made. We revisit the hidden-gauge formalism in coupled channels and the predictions made about states with (I=0;C=1;S=-1), (I=0;C=2;S=0,1) and (I=1;C=0;S=-1). Some of these states could be bound states, resonances or just cusps since they emerge around the energy of the threshold. We discuss these predictions and propose different reactions where the spin partners of the observed states could be observed.
The primary motivation of the GlueX experiment at Jefferson Lab is the search for light hybrid mesons that are quark-antiquark pairs coupled to a gluonic field excitation.
GlueX uses a $\approx 9\;\mathrm{GeV}$ linearly-polarized real photon beam incident on a $\mathrm{LH}2$ target and a solenoid-based, large-acceptance detector. The facility completed the initial phase of data taking in 2018 and has many analysis efforts well underway.
These studies include searches for the $\pi_{1}\;(1600)$ hybrid meson with exotic $J^{PC}=1^{-+}$. There is strong evidence for $J^{PC}=1^{-+}$ resonance reported from studies of $\eta^{\left( '\right) }\pi$ systems. At GlueX we are studying contributions of resonances with different spins in the mass spectrum of the $\eta^{\left( '\right) }\pi$ system via partial wave analysis, where we use a newly developed model for photo-production via linearly polarized beam. There are parallel studies of $\eta^{\left( '\right) }\pi$ system, by considering various production and decay modes ($\gamma p\rightarrow p \eta \pi^{0}, \gamma p\rightarrow \Delta^{++} \eta \pi^{-}, \gamma p\rightarrow p \eta^{'} \pi^{0}, \gamma p\rightarrow \Delta^{++}\eta^{'}\pi^{-}$).
The status of these efforts will be reported.
The Relativistic Heavy Ion Collider (RHIC) is the only collider in the world that is capable of colliding heavy ion and polarized proton-proton beams. RHIC has been producing high-impact results for more than two decades. In this talk, I will present some of the recent RHIC results from PHENIX and STAR experiments. I will also provide a future outlook as we complete the RHIC science mission with sPHENIX coming online and STAR with forward upgrades, and transition into the future Electron-Ion Collider (EIC). Brookhaven Lab’s role in the work of the EIC and the work and operations at RHIC are supported by the DOE Office of Science (NP). Brookhaven National Laboratory is supported by the U.S. Department of Energy’s Office of Science.
Neutron stars and explosive astrophysical systems - such as supernovae
or compact star binary mergers - represent natural laboratories where
extreme states of baryonic matter are populated. Modeling such
environments assumes, among others, good understanding of zero and
finite temperature equations of state (EoS). In this talk I shall first
discuss the relation between nuclear matter EoS and neutron star
properties. Then I shall review thermal properties of a number of
general purpose EoS. Properties of purely nucleonic EoS will be
confronted with properties of EoS which account for hyperons, meson
condensates, Delta-resonances and quarks. Correlations with parameters
of nuclear matter will be discussed along with the dependence on the
theoretical framework.
The NA62 experiment at CERN collected world's largest dataset of charged kaon decays in 2016-2018, leading to the first observation of the ultra-rare K+ --> pi+ nu nu decay based on 20 candidates. Dedicated trigger lines were employed for collection of di-lepton final states, which allowed establishing stringent upper limits on the rates lepton flavor and lepton number violating kaon decays. The dataset is also exploited to search for production of light feebly interacting particles (such as heavy neutral leptons) in kaon decays. Recent NA62 results based on the 2016-2018 dataset, and the prospects of the NA62 experiment, are presented.
We will discuss the reach for light new physics in rare kaon and hyperon decays.
The Belle II experiment at the SuperKEKB energy-asymmetric electron-positron collider is a major upgrade of the B factory experiment at KEK in Tsukuba, Japan. With a goal of collecting 50 times the data recorded by its predecessor, Belle II has an expansive program in hadronic spectroscopy. Many early measurements have proven the capabilities of the detector. In this talk, I will review some recent measurements related to how we can use weak reactions to learn about hadron interactions, as well as first results from unique datasets and projections for future studies.
A theoretical analysis of the $C\!$-conserving semileptonic decays $\eta^{(\prime)}\to \pi^0 l^+ l^-$ and $\eta^{\prime}\to \eta l^+ l^-$ ($l=e$ or $\mu$) is carried out within the framework of the Vector Meson Dominance (VMD) model. A phenomenological model is used to parametrise the VMD coupling constants and the associated numerical values are obtained from an optimisation fit to $V\to P\gamma$ and $P\to V\gamma$ radiative decays ($V=\rho^0,\omega,\phi$ and $P=\pi^0,\eta,\eta^\prime$). Finally, the signature of $C\!P$ violating operators from the SMEFT on experimental observables is investigated and quantified for the $l=\mu$ case.
I will summarize some of the recent results in meson spectroscopy in the light and heavy sectors, in particular for exotic candidates.
Stunning discoveries of the hadronic states,
$P_{\psi}$, $P_{\psi s}$, $T_{\psi}$, $T_{\psi s}$, and $T_{\psi\psi}$, that are manifestly different to the conventional meson and baryons, have energized the field of spectroscopy in recent years. New exotic states keep appearing thanks to the excellent detector performance of the LHCb experiment and scrupulous data analysis. In this talk, fresh findings of new states, $T_{cs}$, $T_{c\bar{s}}$, $T_{cc}$ and possibly $T_{\psi\phi}$ at LHCb will be discussed.
In this talk I summarize advances on calculations of hadron spectrum and structure observables using functional methods such as Dyson-Schwinger and Bethe-Salpeter equations. Systematic improvements in this approach have made it possible to address a wide range of problems from the baryon excitation spectrum to multiquark spectroscopy, form factors, parton distributions and other areas. I will make a survey through some open questions in QCD, with an emphasis on the structure of exotic hadrons and multiquarks, and connect them with key underlying phenomena such as mass generation for quarks and gluons.
Using a scan sample taken at center-of-mass energies from 3.773 GeV to 4.95 GeV with an integrated luminosity of 22/fb, the properties of XYZ states are investigated at BESIII. The cross sections of $e^+e^- \rightarrow D^{*+} D^{*-}$ and $D^{*+} D^-$, $e^+e^- \rightarrow K^+ K^- J/\psi$, and $\pi^+ \pi^- \psi_2(3823)$ are measured. New decay modes of $X(3872) \rightarrow \pi^0 \chi_{c0}$ and $\pi \pi \chi_{c0}$ are searched where the $X(3872)$ is produced via the process of $e^+e^- \rightarrow \gamma X(3872)$.
In this talk we will discuss our recent works (2201.08253 and 2207.08563) in which we make analyses of several X and Z states. In the first part of the talk, we present a combined study of the BESIII spectra in which the Z_{c}(3900) and Z_{cs}(3985) states are seen, assuming that both are SU(3) partners. In the second part, a step further is taken and we analyze the full heavy quark spin and light flavor multiplets arising by considering as inputs the X(3872), Z_{c}(3900), and the X(3960) recently claimed by LHCb in the D^{+}_{s} D^{-}_{s} spectrum.
The $X_0(2900)$ was observed by the LHCb and has been largely accepted as a $D^* \bar K^*$ molecule. Yet, the molecular picture gives rise to three spin states, with $J^P=0^+,1^+,2^+$, and only the $0^+$ state has been so far observed.
We present three methods to determine these extra states.
1) The $\bar B^0 \to D^{∗+} ̄\bar D^{*0} K^−$, looking at the $D^{*+} K^-$ spectrum.
2) The $\bar B^0 \to K^0 D^{*+} K^−$, reaction, also looking into the $D^{*+} K^-$ spectrum
These two methods are meant to detect the $1^+$ state. The $2^+$ state is suggested to be formed in the $B^+ \to D^{+} D^{-} K^{+} $ reaction, constructing different momenta of the $D^{-} K^{+}$ mass distributions.
Rates for the signal and background in these reactions have been calculated and found to be at reach in LHCb and other facilities.
Refs. : Phys.Lett.B 832 (2022) 137219 ; Phys.Rev.D 105 (2022) 9, 096022 ; 2207.02577
Elastic lepton-nucleon scattering is arguably the simplest measurable process sensitive to the nucleon's internal structure and dynamics. The spacelike and timelike electromagnetic form factors of the nucleon have been measured with ever increasing precision over a wide range of energies since the 1950's, and these measurements have led to many surprises and discoveries that changed our basic notions of nucleon size, shape, and structure. In this talk I will present an overview of nucleon electromagnetic form factors, including their theoretical definition, their relation to experimental observables, the history and current status of the experimental data over the entire range of momentum transfer Q^2, and the major outstanding questions to be addressed by improved theoretical calculations and future experiments at low and high energies.
The JLab 12-GeV electron beam provides an opportunity to advance Q2 for all four electro-magnetic form-factors. Currently the results for GMp up to 15 GeV2 are published, and the data for GMn up to 13.5 GeV2 are collected. The Hall B GMn experiment also collected new data. In 2022-23 the GEn experiment will collect data for Q2 up 9.9 GeV2 and after that the data for GEp will be obtained up to 12 GeV2. In addition, there is a proposal to measure the weak form-factors at 2.5 GeV2 to allow reduced uncertainty of flavor decomposition analysis. We will discuss the setup and the results of these experiments.
Hadronic matrix elements of the QCD energy-momentum tensor can be parametrized in terms of gravitational form factors (GFFs), which encode information about mechanical properties of the hadron like the spatial distributions of energy, pressure, and shear forces. GFFs can be constrained indirectly by experiments through their relation with generalized parton distributions (GPDs), but they are directly and straightforwardly accessible to lattice calculations. We present the results of recent lattice calculations of the GFFs in the proton, including a complete calculation of both quark and glue contributions, and use them to derive spatial densities.
Nucleons are one of the most fundamental building blocks of ordinary matter, yet their internal structure and dynamics are still not fully understood. Electromagnetic form factors allow to investigate fundamental properties of the nucleon. The BESIII collaboration has studied the time-like form factors of the proton using the energy scan and the ISR technique. The |GE/GM| ratio is obtained with a precision comparable to the investigations of the space-like EMFF in electron proton scattering. The effective form factor of the neutron is measured with highest precision using the scan method. For both nucleons, an intriguing periodic behavior of effective form factors lineshape is observed. In this presentation the latest results on nucleon form factors at BESIII are discussed.
Time-like hadron electromagnetic form factors are accessible through electron-positron annihilation into a hadron and anti-hadron pair and its time reverse reaction. Large progress was recently done at electron-positron colliders, applying the Initial State Radiation (ISR) method. Precise measurements of the proton form factor, up to s $simeq$ 40 GeV$2$, done by BaBar showed irregularities in the annihilation cross section and in the effective form factor spectra. These structures were recently confirmed by BESIII with both, ISR and beam scan methods. When plotted as a function of the relative momentum of the produced hadrons, this behavior can be fitted by a damped regular oscillation on the top of a monotone decreasing background, favoring a description in terms of an interference between phenomena occurring at the quark scale (0.2 fm) and at the hadron scale (1 fm). A similar analysis done by the BESIII collaboration, highlights such behavior also in the neutron case. Interesting correlations appear among proton, neutron and hyperon form factors.
I discuss neutron star matter from the picture of quark-hadron continuity. Recent neutron observations indicate that 2.1- and 1.4-solar mass neutron stars have similar radii, disfavoring the presence of strong first order phase transitions in the domain between ~2n0 and ~5n0 with n0 being nuclear saturation density. Meanwhile ~5n0 is the density where baryons are expected to overlap and therefore may be regarded as quark matter. These considerations together lead us to the scenario of quark-hadron continuity. I argue how the sound velocity peak follows from this conjecture, emphasizing the importance to keep track of quark states from nuclear to quark matter.
The Equation of State (EoS) links together fundamental properties of nuclear matter. Heavy nuclei, though orders of magnitude smaller than neutron stars, are governed by the same underlying physics, which is enshrined in the EoS. An accurate and model-independent determination of the neutron-skin thickness of heavy nuclei, using parity-violating electron scattering, provides significant constraints on the density dependence of the nuclear symmetry energy, a key parameter of the EoS. The currently most precise determination of the neutron-skin thickness of $^{208}$Pb by the PREX collaboration suggests that the EoS at nuclear densities is stiff, which is in slight tension with the prediction based on astronomical measurements. To help clarify this tension, the Mainz Radius EXperiment (MREX) at MESA will determine the neutron-skin thickness of $^{208}$Pb with unprecedented precision. Status and prospects of the parity-violation measurement program will be presented.
The PREX and CREX experiments at Jefferson Laboratory use parity violating electron scattering to cleanly locate neutrons in neutron rich nuclei. These measurements demonstrate that heavy nuclei have a neutron rich skin and measure its thickness. This determines the pressure of neutron rich matter and has important implications for the structure of neutron stars. We compare PREX results in the laboratory to neutron star observations with X-rays and gravitational waves
Recent measurement of coherent π0 photoproduction on Pb lead to a most accurate determination of the neutron skin, constraining nuclear matter Equation of State (EoS) at around ρ~1ρ0. A natural next step is elucidating the nuclear EoS at higher densities to tune our understanding of the most violent process in the Universe - neutron stars mergers. It was demonstrated that at densities above ~3ρ0 dibaryonic degrees of freedom come into play [1]. The work presented in this talk is aiming to improve our knowledge of dibaryon behavior in dense nuclear matter by measuring coherent π0π0 photoproduction off Ca-40/48 nuclei. The experiment was performed at the A2@MAMI facility in Mainz (Germany). The goal of the analysis is to identify the first genuine hexaquark, the d(2380), photoproduction on nuclei. We are expecting to determine the medium modifications of the d(2380) in nuclear matter and constrain its couplings [2]. These new results will further improve our understanding of the neutron stars equation of state and allow precise determination of the maximum neutron star mass as well as provide key ingredients for calculation of the neutron stars merger dynamics. Also, an interplay between the hexaquark, quark-gluon and hyperon degrees of freedom in the EoS of a dense nuclear matter will be discussed. The effective coupling constants obtained in this experiment can further constrain the possibility of hexaquark condensate dark matter [3].
[1] I. Vidana, M. Bashkanov, D.P. Watts, A. Pastore, Phys. Lett. B 781, 112-116 (2018)
[2] A. Mantziris, A. Pastore, I. Vidana, D.P. Watts, M. Bashkanov, A.M. Romero, Astronomy & Astrophysics A40, ISSN 0004-6361 (2020)
[3] M. Bashkanov, D.P. Watts 2020, J. Phys. G: Nucl. Part. Phys. 47 03LT01 (2020)
Short-Range Correlations (SRCs) between nucleons appear to a ubiquitous feature of the structure of nuclei. While correlated nucleons are a minority (estimated to be approximately 20% of nucleons in all but light nuclei), they can have an outsized influence on a number of relevant nuclear properties such as the symmetry energy in the nuclear matter equation of state, matrix elements in double beta decay, and the modification of nucleon partonic structure by the nuclear medium. For this reason, several recent and upcoming experiments at Jefferson Lab aim to address several key open questions that will improve our understanding the structure and dynamics of SRCs. CLAS12's Run Group M recently made a high statistics measurements of SRC break-up reactions on a wide range of nuclei to address, among a myriad of questions, the possibility of three-nucleon correlations. A recent measurement in Hall D was the first use of photoproduction to study SRCs, helping to answer questions about reaction mechanisms and probe-independence. The BAND Experiment at CLAS12, currently under analysis, seeks to address the role of SRCs in the EMC Effect. These and other upcoming experiments will be reviewed.
Neutrino oscillation experiments rely on observing neutrino-nucleus interactions to obtain the energy spectrum which is key to study this phenomenon. The challenge in obtaining the required precision lies in controlling the systematic uncertainties in the energy measurement of the neutrinos. A significant fraction of these uncertainties comes from the unknowns of neutrino scattering. A better understanding of neutrino-nucleon interactions is critical to enhance the precision of neutrino oscillations measurements. In this talk I will describe recent progress in the study of neutrino interactions and the remaining uncertainties related to nuclear effects.
We are entering an era of high-precision neutrino oscillation experiments (T2HK, DUNE), which potentially hold answers to some of the most exciting questions in particle physics. Their scientific program requires a precise knowledge of neutrino-nucleus interactions coming from fundamental nuclear studies. These theoretical calculations should be firstly benchmarked with electron scattering data.
In my talk I will give an overview of the recent progress that has been made in describing electron-nucleus scattering within the ab-initio coupled-cluster framework, combined with the Lorentz integral transform. These techniques open the door to obtaining electroweak nuclear responses (and consequently cross-sections) for medium-mass nuclei starting from first principles.
Hadronic molecules are composite systems of hadrons. Many hadron resonances observed in the last two decades are good candidates of hadronic molecules, including the X(3872), the hidden-charm Pc pentaquarks, the double-charm Tcc, etc. I will discuss the physics of hadronic molecules with a focus on the hidden-charm and double-charm ones.
The LHCb collaboration recently discovered a doubly charmed tetraquark $T_{cc}$ with flavor $cc\bar u\bar d$ just below $DD^*$ threshold. This is the longest lived hadron with explicitly exotic quark content known to this date. We present the first lattice QCD study of $DD^*$ scattering in this channel, involving rigorous determination of pole singularities in the related scattering amplitudes. Working with a heavier than physical light quark mass, we find a signature for a shallow virtual bound state pole in the $DD^*$ scattering amplitude with $l=0$, which is likely related to $T_{cc}$. The dependence of this state on the quark masses is also discussed.
Our understanding of the physics of baryonic systems containing strangeness is limited by the scarcity of experimental data. Aiming at alleviating this deficit is lattice QCD, a numerical approach to solve the complex dynamics of strongly interacting systems of hadrons and nuclei. In this talk I will present the results obtained by the NPLQCD collaboration for two octet-baryon systems, with strangeness ranging from 0 to -4, with findings that point to interesting symmetries observed in hypernuclear forces as predicted in the limit of QCD with a large number of colors, and also recent results from a variational study using a wide range of interpolating operators.
Understanding the dynamics of hadrons with different quark content is crucial to solve fundamental aspects of QCD as well as for the implications on the structure of dense stellar objects, such as neutron stars. The scarce statistics and lack of data in reactions for unstable hadrons, containing in particular strange and charm quarks, affect the accuracy of the current theoretical description of the corresponding strong interaction. Additionally, the modelling of nuclei and hypernuclei requires a precise knowledge of three-body forces, for which a direct measurement is still missing.
In the past several years the use of correlation techniques, applied to particle pairs produced in high-energy collider experiments, have been proven capable of complementing and expanding our existing knowledge of the hadronic interactions, particularly in the strangeness sector. The present contribution provides an overview of the milestones reached by the ALICE Collaboration using the femtoscopy technique in pp collisions at $\sqrt{s}$ = 13 TeV. The main highlights are the unprecedented precision studies of the interaction of baryons containing strange and charm quarks, alongside the extension of the analysis methods into the three-body sector to experimentally isolate the three-body interaction contribution.
In this article, we study simple hadron scattering models provided by the PYTHIA8 Monte Carlo event generator, intended to consider the overlap of multiple strings at low transverse dimensions. Firstly, we studied a so-called new model for generating the transverse momentum of hadrons during the string fragmentation process. Secondly, close packing of strings is taken into account by making the temperature or string tension environment-dependent. Thirdly, a simple model for hadron scattering is added. The effect of these models is studied, individually and then compared these three models collectively with data from the LHC.
Exploring the electromagnetic form factors of baryons helps us understand their internal structure and how the strong force binds the quarks together. The form factors of nucleons have been and continue to be studied extensively, but it is valuable to also pursue other, parallel avenues of research. A complementary and relatively unexplored approach is the study of hyperons. What does the presence of the heavier strange quark mean for the structure and what does this, in turn, tell us about the strong force? Answering these questions allows us to form a more general and complete understanding of how baryons are formed. The instability of hyperons makes measurements of their form factors difficult compared to those of the nucleons, but because their decays are "self-analyzing" they also offer unique opportunities. In this talk I will discuss how polarization, entanglement, and self-analyzing decays can be combined to measure the electromagnetic form factors of hyperons, and how these measurements can be interpreted in terms of structure. Finally, I will show recent results from the BESIII experiment where this method has been applied to the $\Lambda$ hyperon.
Radiative transition of an excited baryon to a nucleon with emission of a virtual massive photon converting to dielectron pair (Dalitz decays) provides important information about baryon-photon coupling at low q2 in timelike region. These measurements are complementary to time like e+e- annihilation experiments at larger q2 value and meson production with electron and photon beams covering space like region. In this talk an extension of the HADES programme on non-strange baryons (see B. Ramstein) for Hyperons will be presented. Perspective for Dalitz decays of L(1520)/S(1385)->Lambda e+e- in high statistical run with p+p at 4.5 GeV will be given. Furthermore, results for L(1520)->Lambda pi+pi decay from p+p at 3.5 GeV will be given. They provide valuable constraints on isospin=0/1 contribution to Dalitz decay.
We consider the chiral Lagrangian with nucleon, isobar, and pion degrees of freedom. The baryon masses and the axial-vector form factor of the nucleon are derived at the one-loop level. We explore the impact of using on-shell baryon masses in the loop expressions. As compared to results from conventional chiral perturbation theory we find significant differences. An application to QCD lattice data is presented. We perform a global fit to the available lattice data sets for the baryon masses and the nucleon axial-vector form factor, and determine the low-energy constants relevant at N$^3$LO for the baryon masses and at N$^2$LO for the form factor. Partial finite-volume effects are considered. We point out that the use of on-shell masses in the loops results in non-analytic behavior of the baryon masses and the form factor as function of the pion mass, which becomes prominent for larger lattice volumes than presently used.
The spin content of the proton as a function of quark and gluon helicities and orbital angular momentum can be described in terms of integrals of parton distributions. These integrals, from x=0 to 1, require in particular a precise understanding of the asymptotic behavior of said distributions in the low x limit. We will discuss the resummation of double logarithms which governs this behavior and its consequences on the proton spin problem.
In this talk we present our BK solution to next-to-leading order approach (NLO) and compare with the experimental HERA data. This approach includes the re-summed NLO corrections to the kernel of the evolution equation, the impact
parameter dependence of the saturation scale in accord with the Froissarrt theorem as well as the non-linear corrections. We successfully describe the experimental data with the quality, which is not worse, than in the leading order fits with larger number of the phenomenological
parameters. It is demonstrated, that the data could be described, taking into account both the diffusion on ln(kT ), which stems from perturbative QCD, and the Gribov’s diffusion in impact parameters.
The gravitational-wave observatories of LIGO and Virgo have opened a new field of astronomy. The first and nearest signal from merging neutron stars, GW170817, guided astronomical partners' observations, constrained the source system's properties, and gave a new viewpoint on the equation of state of dense matter in neutron stars. More distant sources primarily tell us about the source masses, and additional mergers involving neutron stars have already revealed that gravitational-wave sources are unlike binaries previously observed in our Galaxy. Together gravitational-wave observations are informing our understanding of dense matter and stellar evolution. In this talk, I will outline prospects of learning about neutron stars in the current Advanced-detector era and show how current results fit with other observations of dense matter and nuclear physics. I will extrapolate to the astronomical potential of next-generation ground-based observatories like Cosmic Explorer.
In the relativistic mean-field Quark-Meson-Coupling (QMC) model, the baryon-baryon interaction in medium is interpreted in terms of a virtual meson exchange between light valence quarks in individual baryons [1]. This unique feature leads to a dramatic reduction of variable parameters of the model as compared to traditional nuclear structure models, and to a versatile application to high density matter in compact objects as well as to a wide range of properties of finite nuclei [2]. In this presentation, I will focus on the QMC predictions of the Equation of State of cold and hot matter in neutron stars and supernovae [3]. Composition of the matter, including leptons and heavy strange baryons, its density and temperature dependence and its effects on the maximum mass of cold neutron stars, the speed of sound and rotation properties will be discussed.
[1] P.A.M. Guichon, J.R. Stone and A.W. Thomas, Prog.Part.Nucl.Phys., 100, 262 (2018)
[2] K. L. Martinez, A. W. Thomas, J.R.Stone, P.A.M.Guichon, PRC 100, 024333 (2019) [3]
[3] J. R. Stone, V. Dexheimer, P. A. M. Guichon, A. W. Thomas and S. Typel, MNRAS 502, 3476–3490 (2021)
We obtain the equation of state (EoS) for two-color QCD at low temperature and high density from the lattice Monte Carlo simulation. We find that the velocity of sound exceeds the relativistic limit (cs2/c2=1/3) after BEC-BCS crossover in the superfluid phase. Such an excess of the sound velocity is predicted by several effective theories but is previously unknown from any lattice calculations for QCD-like theories. This finding might have possible relevance to the EoS of neutron star matter revealed by recent measurements of neutron star masses and radii.
We construct posterior distributions of equations of state (EoS),
relevant to the studies of neutron stars (NSs), by applying Bayesian
approach to two different models. The EoSs are subjected to minimal
constraints which correspond to a few basic properties of nuclear
matter at the saturation density and the low density pure neutron
matter EoS obtained from a precise next-to-next-to-next-to-leading
order (N$^{3}$LO) calculation in chiral effective field theory. The tidal deformability and radius of neutron star over a wide range of mass are found to be strongly co-related with pressure of $\beta$-equilibrated matter as well as the symmetry energy at densities higher than the saturation($\rho_0$) density in a model independent manner. These correlations are employed to parametrized the pressure for $\beta$-equilibrium matter, around 2$\rho_0$, as a function of neutron star mass and the corresponding tidal deformability.The maximum mass of neutron star is also strongly correlated with pressure of $\beta$-equilibrated matter and symmetric nuclear matter at densities $\sim$ 4.5$\rho_0$. The combined effects of available bounds on the NS properties in constraining the EoS are also explored.
Based on the 4.48x10^6\psi(3686) events, we will report on searches for the decay \psi(3686) and chi_cJ ->Lambda anti-Lambda, chi_cJ-> nK_S Lambda +c.c., and isospin violation decay \psi(3686) -> Lambda anti-Lambda pi0. Using data events of integrated luminosity 3.18/fb taken at sqrt s= 4.18 GeV, the decay e^+e^- -> pK anti-Lambda bar +c.c. is analyzed with partial wave analysis. The contributions from excited Lambda and N* states will be reported.
A detailed study of the nucleon resonances and their decays is an essential step towards exploring the low energy region of QCD. By analysing the excitation spectrum of (quasi-) free nucleons we are able to establish a baseline for comparisons with in-medium modifications. Of particular interest are the mixed-charged channels of double-pion photoproduction, as they are sensitive to sequential decays of $\Delta$ resonances, but also to the charged $\rho$ channel. The coupling to a $\rho$ could induce substantial in-medium effects when the $\rho$ spectral function is modified in the medium. Recent results from data taken with the A2 experiment at MAMI are presented and compared to recent MAID model calculations up to beam energies of 1500 MeV. The unpolarized cross sections could be obtained by collecting data with a liquid hydrogen target. The analysis shows a significant contribution of the $\rho$ channel to the second resonance peak.
Phenomenological amplitudes obtained in partial-wave analyses of single-pion photoproduction are used to evaluate the contribution of this process to the Gerasimov--Drell--Hearn (GDH), Baldin, and Gell-Mann--Goldberger--Thirring (GGT) sum rules, by integrating up to 2 GeV in photon energy. Our study confirms that the single-pion contribution to all these sum rules converges even before the highest considered photon energy, but the levels of saturation are very different in these three cases. Single-pion production almost saturates the GDH sum rule for the proton, while a large fraction is missing in the neutron case. The Baldin integrals for the proton and the neutron are both saturated to about four fifths of the predicted total strength. For the GGT sum rule, the wide variability in predictions precludes any definitive statement.
We have performed calculations for the states $\Omega_{cc}$, $\Omega_{bc}$ and $\Omega_{bb}$ stemming from coupled channel interactions between the pseudoscalar or vector mesons and the $1/2^+$, $3/2^+$ baryons. In all cases, we find bound states or resonances, using the Bethe-Salpeter equation to unitarize the interaction of the coupled channels with the input for the potential obtained from an expression of the local hidden gauge approach to the charm and beauty sectors. These states are presently under investigation by the LHCb Collaboration.
The Electron-Ion Collider (EIC), a powerful new facility to be built in the United States at the U.S. Department of Energy’s Brookhaven National Laboratory in collaboration with Thomas Jefferson National Accelerator Facility, will explore the most fundamental building blocks of nearly all visible matter. The EIC will address some of the most profound questions concerning the emergence of nuclear properties by precisely imaging gluons and quarks inside protons and nuclei like their distributions in space and momentum, their role in building the nucleon spin and the properties of gluons in nuclei at high energies. In January 2020 the EIC received CD-0 and Brookhaven National Laboratory was selected as site, and June 2021 CD-1 was granted to the EIC Project. In this talk I will review the science capabilities of the EIC and discuss the status and ongoing efforts towards its realization.
The accelerator facility for Antiproton and Ion Research FAIR, one of the largest research infrastructures in Europe, is currently being built adjacent to the campus of GSI, Helmholtzzentrum für Schwerionenforschung, in Darmstadt. A suit of accelerators and storage rings will offer excellent research opportunities in hadron and nuclear physics, in atomic physics and nuclear astrophysics as well as in applied sciences like materials research, plasma physics and radiation biophysics with applications towards novel medical treatments and space science. FAIR is an international facility with 10 partner countries. More than 2500 scientists and engineers from more than 50 countries are involved in the preparation and definition of the research at FAIR. Science of FAIR is organized in four pillars: PANDA is a large experimental set-up to study proton-antiproton collisions; NUSTAR represents the nuclear structure, nuclear reaction and astrophysics community and is focused on the exotic isotope facility Super-FRS; CBM stands for the exploitation of dense baryonic matter with heavy ion collisions, and atomic physics, plasma physics and applied science are gathered within the APPA pillar. While the full potential of FAIR can only be exploited once the accelerators have been constructed and become operational, some of the experimental instrumentations are already available and are being utilized in a dedicated research program FAIR Phase-0 at GSI, exploiting the upgraded accelerator chain at GSI, and the international collaborations are intensively preparing the Day-1 program at FAIR.
The scientific potential of FAIR will be presented in this talk and the status of the construction will be summarized with a special focus on the activities and the scientific results of FAIR Phase-0.
The ability of current and next generation accelerator based neutrino oscillation measurements to reach their desired sensitivity and provide new insight into the nature of our Universe, requires a high-level of understanding of the neutrino-nucleus interactions. These include precise estimation of the relevant cross sections and the reconstruction of the incident neutrino energy from the measured final state particles. Incomplete understanding of these interactions can skew the reconstructed neutrino spectrum and thereby bias the extraction of fundamental oscillation parameters and searches for new physics.
This talk will explore what we know of the neutrino-nucleus interaction, browse through the methods used for its simulate, and discuss ways to constrain their uncertainties with both neutrino and electron scattering data.
I give an overview of (some of) the different analysis tools and PWA approaches used to extract the spectrum of nucleon and Delta states from experimental data. Differences and similarities, e.g. in the construction of the amplitude or the data base, will be illustrated.
In addition, I will discuss the current status of the hyperon resonance spectrum.
Artificial Intelligence (AI) and Machine Learning (ML) are rapidly developing fields providing data-driven algorithms to predict, classify, and make decisions based on data. ML techniques are widely used across the physical sciences in order to learn from the vast amount of data collected and have been implemented in nearly every aspect of Nuclear Physics research. In contrast to traditional analysis tools, these algorithms often use less computing resources, can learn from sparse data, and are less prone to human errors. This talk will summarize current applications of ML in experimental and theoretical nuclear physics, as well as accelerator applications, with a special emphasis on interpretability and uncertainty quantification.
Jefferson Lab is considering extending the fruitful physics program carried out at 6GeV and 12 GeV electron beam with new infrastructure. A unique positron beam of high intensity and high polarization up to 12 GeV energy will open new opportunities in exclusive reaction channels (DVCS) and precision (two-photon exchange) and BSM physics (Dark Matter searches). Existing detectors upgrade to run at higher luminosity, as well as plans to extend the electron beam energy to 24 GeV are also discussed in a series of workshops supported by the lab leadership and the user community. In this contribution, I will give an overview of the physics opportunity with the upgraded CEBAF at JLab and plans to make it real.
A beam of neutral kaons at the GlueX experiment will provide exciting physics opportunities for baryon and meson spectroscopy. With a flux exceeding previous experiments by up to three orders of magnitude, the approved K-Long facility at Jefferson Lab will allow us to substantially improve our knowledge of the properties of strangeness $S=-1$ hyperons by providing input for partial-wave analyses. Such coupled-channel studies of $2\to 2$ reactions will be enabled through the measurement of different final states over an energy range covering the spectrum of excited baryons.
This will allow the testing of chiral-unitary models for the $\Lambda(1405)$ at low energies, quark models, and lattice QCD predictions over the entire resonance region. In addition, the under-explored territory of $S=-2$ and $S=-3$ baryons will be mapped with a distinct potential for the discovery of many unseen states predicted by theory. The measurement of associated multi-meson final states is also necessary for the extraction of much improved pion-kaon amplitudes covering, in particular, lower energies. This is crucial to pin down the enigmatic $\kappa$ resonance, and to provide much-needed input to better understand SU(3) chiral perturbation theory and the pattern of QCD spontaneous chiral symmetry breaking.
sPHENIX is a new collider detector at the Relativistic Heavy Ion Collider, with a commissioning and first data-taking run taking place in Spring 2023. The experiment is purpose-built for state-of-the-art jet and heavy flavor probes of the Quark-Gluon Plasma, with qualitatively new capabilities not previously available at RHIC. This talk will give an overview of the sPHENIX physics program and the status of the final construction and integration of the detector.
The STAR Collaboration has successfully completed an upgrade consisting of forward detector systems located between 2.5 < η < 4.0. This upgrade comprises a Forward Calorimeter System, containing an Electromagnetic Calorimeter and a Hadronic Calorimeter, and a Forward Tracking System, consisting of a Forward Silicon Tracker and Forward small-strip Thin Gap Chambers. The forward detector upgrade has excellent detection capability for neutral pions, photons, electrons, jets, and charged hadrons.
A combination of soft and hard probes collected during 2023-25 will be used to probe the QGP’s microstructure and will enable a unique forward physics program via the collection of high statistics Au+Au, p+Au, and p+p data at sqrt(s_NN) = 200 GeV. With the extended acceptance and the enhanced statistics, STAR will be positioned to perform correlation studies in heavy-ion collisions, e.g., the pseudorapidity dependence of azimuthal correlations and the pseudorapidity dependence of global hyperon polarization. The STAR forward detector upgrade will also enable an extensive suite of measurements probing the quark-gluon structure of heavy nuclei.
In this talk, we will present the current status of the forward detector system and discuss its performance during data taking with cosmic ray and p+p collisions at sqrt(s_NN) = 510 GeV during the 2022 RHIC run.
SPD is an international experiment primarily focused on study of the
spin-dependent gluon structure of proton and deuteron in $pp$, $pd$, and $dd$
collisions. The experiment will operate on polarized beams of the NICA
facility at Joint Institute for Nuclear Research. The accelerator
complex can provide beams with the center-of-mass energy $\sqrt{s_{NN}}$
up to 27 GeV for $pp$ collisions, and up to 13.5 GeV for $dd$ collisions.
The talk will give an overview of the project goals, status,
experimental set-up, expected performance of the SPD detector, and
tentative running strategy.
The Muon g-2 Experiment at Fermi National Accelerator Laboratory was designed to measure the anomalous magnetic moment of the muon, a, with a target precision of 140 parts-per-billion; a four-fold improvement over the former measurement from the early 2000s at Brookhaven National Laboratory. The experiment was motivated by the ~3.5 standard deviation between the BNL result and the Standard Model prediction of a; which could be a hint of new physics. The first result at Fermilab from the Run-1 data taking period has achieved an uncertainty of 460 parts-per-billion and confirmed the BNL discrepancy, further increasing the tension with the Standard Model. The talk will give an overview of the status of the Standard Model prediction, the experimental technique, key aspects of the measurement, and the data analysis.
The system of light pseudoscalar meson π0, η and η' provide a unique laboratory to probe fundamental QCD symmetries at the confinement scale. While π0 and η are Goldstone bosons due to spontaneous chiral symmetry breaking, η' is not due to an axial U(1) anomaly. There is a second type of chiral anomaly driving the two-photon decays of these mesons. This system harbors information about the effects of SU(3) symmetry and the mixing phenomena of the mesons due to isospin symmetry breaking. A study of this system will have important impact on the low-energy QCD: testing the chiral anomaly and probing the origin and dynamics of chiral symmetry breaking; offering a clean path for model independent determinations of the light quark-mass ratio and the η-ηꞌ mixing angle; and providing inputs to calculate the hadronic light-by-light scattering corrections to the anomalous magnetic moment of the muon. A comprehensive experimental program has been developed at Jefferson Laboratory (JLab) to perform high precision measurements of the two-photon decay widths and the transition form factors of π0, η and η' via the Primakoff effect. A measurement of the π0 radiative decay width was carried out at JLab 6 GeV and the published result achieved a precision of 1.5%. A measurement of the η radiative decay width is currently on-going with a 11 GeV tagged photon beam. The status of this program and its physics impact will be discussed.
The world’s largest sample of J/ψ events accumulated at the BESIII detector offers a unique opportunity to investigate η and η′ physics via two body J/ψ radiative or hadronic decays. In recent years the BESIII experiment has made significant progresses in η/η′ decays. A selection of recent highlights in light meson spectroscopy at BESIII are reviewed in this report, including the observation of η′ → π+π−μ+μ−, observation of the cusp effect in η′ →π0π0η, search for CP-violation in η′ → π+π−e+e−, as well as the precision measurement of the branching fraction of η decays.
With almost 8 fb−1, the KLOE and KLOE-2 data sample represents a
unique, physics-rich sample and the largest dataset ever sized at an electron-
positron collider operating at the φ peak resonance. It represents a collection
of about 24 billion of φ mesons, whose decays include about 8 billion pairs
of neutral K mesons and about 300 million η mesons. With this sample, the
KLOE-2 Collaboration carries out a complete, wide hadron physic program by
investigating rare meson decays, γγ interaction and dark forces.
Various models and theories, like VMD (Vector Meson Dominance) or ChPT
(Chiral Perturbation Theory) can be tested with the η → π0γγ golden channel,
which predicted Branching Ratio (BR) differs by far from the experimental
value. With a highly pure η sample produced in φ → ηγ, KLOE-2 has performed
a refined measurement of this BR.
Following a tradition on dark searches initiated by KLOE; KLOE-2 takes the
witness by testing an opposite model to the U boson or ”dark photon”, where
the dark force mediator is an hypothetical leptophobic B boson that could show
up in the φ → ηB → ηπ0γ , η → γγ channel. The analysis and the preliminary
upper limit on the αB coupling constant will be reported.
A very distinctive feature of KLOE-2 is to allow for the possibility to in-
vestigate π0 production from γγ scattering by tagging final-state leptons from
e+e− → γ∗γ∗e+e− → π0e+e− in coincidence with the π0 in the barrel calorime-
ter. The analysis status and preliminary counting of the γ∗γ∗ → π0 events will
be shown.
KLOE-2 is also performing the search for the double suppressed φ → η π+π−
and the conversion φ → η μ+μ− decays with both η → γγ and η → 3π0 reac-
tions. We will report clear signals, which are seen for the first time.
Lastly, the ω cross section measurement in the e+e− → π+π−π0γISR channel
using the Initial State Radiation (ISR) method will be also presented.
Triangle singularity is one type of S-matrix singularities that appear in a triangle diagram when the interactions at all vertices can take place classically. On the one hand, it can produce a peaking structure mimicking a resonance, and thus its effects need to be carefully analyzed when identifying a new resonance; on the other hand, it can be used for precisely measuring the binding energy of a near-threshold particle. In this talk, I will review the effects of triangle singularities in various hadronic reactions.
We present the properties of open heavy mesons in hot mesonic matter based on a self-consistent theoretical approach that takes into account chiral and heavy-quark spin-flavor symmetries. The heavy-light meson-meson unitarized scattering amplitudes in coupled channels incorporate thermal corrections as well as the dressing of the heavy mesons with the self-energies [1, 2]. As a result, the open heavy-flavor ground-state spectral functions broaden and their peak is shifted towards lower energies with increasing temperatures. This has strong implications for the excited mesonic states generated dynamically in this heavy-light molecular model. In addition, we show the meson Euclidean correlators calculated using the thermal ground-state spectral functions obtained within our approach and compare them with recent calculations of lattice correlators [3]. We also report on heavy-flavor transport coefficients below the deconfinement transition computed using the thermal scattering amplitudes and their comparison with lattice calculations and Bayesian analyses in the deconfined phase [4].
[1] G. Montaña, A. Ramos, L. Tolos and J. M. Torres-Rincon, Phys. Lett. B 806 (2020), 135464 doi:10.1016/j.physletb.2020.
[2] G. Montaña, A. Ramos, L. Tolos and J. M. Torres-Rincon, Phys. Rev. D 102 (2020) 9, 096020 doi:10.1103/PhysRevD.102.096020
[3] G. Montaña, O. Kaczmarek, L. Tolos and A. Ramos, Eur. Phys. J. A 56 (2020) 11, 294 doi:10.1140/epja/s10050-020-00300-y
[4] J. M. Torres-Rincon, G. Montaña, A. Ramos and L. Tolos, Phys. Rev. C 105 (2022) 2, 025203 doi:10.1103/PhysRevC.105.025203
Over the past two decades, a large number of exotic states has been discovered at various accelerator facilities. Many of these states are located close to certain hadron-hadron thresholds and therefore can be considered as potential candidates for hadronic molecules. In this talk, we will review the classical Weinberg formalism that was developed to assess whether the deuteron is composite or elementary, and discuss how it can be extended to estimate compositeness of exotic states. We discuss how to treat the effective range parameters extracted from experimental line shapes when coupled channels are present and consider several applications.
We evaluate theoretically the interaction of the open bottom and strange systems $\bar B\bar K$, $\bar B^* \bar K$, $\bar B\bar K^*$ and $\bar B^*\bar K^*$ to look for possible bound states which could correspond to exotic non--quark-antiquark mesons since they would contain at least one $b$ and one $s$ quarks. The s-wave scattering matrix is evaluated implementing unitarity by means of the Bethe-Salpeter equation, with the potential kernels obtained from contact and vector meson exchange mechanisms. The vertices needed are supplied from Lagrangians derived from suitable extensions of the hidden gauge symmetry approach to the bottom sector.
We find poles below the respective thresholds for isospin 0 interaction and evaluate the widths of the different obtained states by including the main sources of imaginary part.
We perform a calculation of the interaction of the $ D \bar{D} $, $ D_{s} \bar{D}_{s} $ coupled channels and find two bound states, one coupling to $ D \bar{D} $ and another one at higher energies coupling mostly to $D_{s}^{+} D_{s}^{-}$. We identify this latter state with the $X_{0}(3930)$ seen in the $D^{+} D^{-}$ mass distribution in the $B^+ \to D^{+} D^{-} K^{+} $ decay, and also show that it produces an enhancement of the $D_{s}^{+} D_{s}^{-}$ mass distribution close to threshold which is compatible with the LHCb recent observation in the $B^+ \to D_{s}^{+} D_{s}^{-} K^{+} $ decay which has been identified as a new state, $X_{0}(3960)$.
The exact eigenenergies of the T4c, T4b, T2bc tetraquarks are calculated within the extended transitional Hamiltonian approach. The IBM, as proposed by Arima and Iachello [1], includes two types of bosons with angular momentum L = 0 (s bosons) and L = 2 (d bosons). To investigate the properties of tetraquarks, similar to that of the two-level system, a four-level system is considered here. To analyze the Quantum Phase Transition between the spherical and rotational limits, similar to Refs. [3-5], the SU(1,1) pairing algebra is introduced. Our results suggest that the pairing strengths are large enough to provide binding; an extended comparison with the current literature is also performed.
[1] A. Arima and F. Iachello, Phys. Rev. Lett. 35, 1069 (1975).
[3] F. Pan and J. Draayer, Nucl. Phys. A 636, 156 (1998)
[4] A. J. Majarshin, Y.-A. Luo, F. Pan, H. T. Fortune, and J. P. Draayer, Phys. Rev. C 103, 024317 (2021).
[5] A. J. Majarshin, Y.-A. Luo, F. Pan, and H. T. Fortune, Phys. Rev. C 104, 014321 (2021).
An overview of the phenomenological aspects of generalized
parton distributions will be given, including recent results and fits
to available experimental data.
The Generalized Polarizabilities (GPs) are fundamental properties of the nucleon. They characterize the nucleon's response to an applied electromagnetic field, giving access to the polarization densities inside the nucleon. As such, they represent a central path towards a complete understanding of the nucleon dynamics. Previous measurements have challenged the theoretical predictions, raising questions in regard to the underlying mechanism responsible for a local enhancement of the electric GP at intermediate four-momentum transfer squared. The measurement of the magnetic GP, on the other hand, promises to quantify the interplay of the paramagnetic and the diamagnetic contributions inside the proton. New results on the proton GPs from the VCS experiment in Hall C at JLab will be presented in this talk.
Generalized Parton Distributions (GPDs) describe the correlations between the longitudinal momentum and the transverse position of the partons inside the nucleon. They are nowadays the subject of an intense effort of research, in the perspective of understanding nucleon spin and mechanical properties.
In this talk, we present the first observation of the Timelike Compton Scattering (TCS) process, $\gamma p\to\gamma^* p^\prime\to e^+e^- p^\prime$, measured using CLAS12 data taken in 2018, with a 10.6 GeV electron beam impinging on a liquid-hydrogen target. The initial photon polarization and the decay lepton angular asymmetries are reported in the range of timelike photon virtualities $2.25<$$Q’^{2}<9$ GeV$^2$ and the squared momentum transferred $0.1<-t<0.8$ GeV$^2$ at the average total center mass energy squared of $\bar{s}=14.5$ GeV$^2$. The polarization asymmetry, similar to the beam spin asymmetry in Deeply Virtual Compton Scattering (DVCS), projects out the imaginary part of the Compton Form Factors (CFF) and provides a way to test the universality of Generalized Parton Distributions (GPDs). The angular asymmetry of the decay leptons, on the other hand, accesses the real parts of the CFF which contain the D-term, a quantity directly linked to the mechanical properties of the nucleon.
The electromagnetic scalar polarizabilities ($\alpha$,$\beta$) are fundamental structure constants of the nucleon, and precise experimental measurements of these are vital for a complete understanding of the nucleon’s internal structure. The scalar polarizabilities can be accessed via Compton scattering reactions on light nuclei targets like $^1$H, $^2$H, and $^3$He. Such cross section measurements can be used to benchmark the chiral effective field theory($\chi$EFT) models. To this end, a series of Compton scattering experiments is underway at the High Intensity Gamma-Ray Source (HI$\gamma$S) at Triangle Universities Nuclear Laboratory, with the goal of extracting the electromagnetic scalar polarizabilities of the neutron ($\alpha_n$, $\beta_n$). The recently completed experiment performed Compton scattering on a liquid deuterium target at incident photon energies of 61 and 81 MeV. Backward-angle scattering cross sections were measured using two large-volume high-resolution NaI detectors. The combined effect of the quasi-monoenergetic beam at HI$\gamma$S and the excellent energy resolution of these detectors was adequate to resolve the inelastic contribution at two backward angles ($115^{\circ}$, $150^{\circ}$). Preliminary elastic and inelastic cross section data at 61 MeV will be presented.
Session: Hadron Structure
Author: Marie Boër, Virginia Tech
Abstract for contributed talk
Generalized Parton Distribution have been studied for many years and are a great tool to approach the multi-dimensional position vs momentum structure of the nucleon. Now, most of the measurements and constraints to GPD models are coming from DVCS (Deeply Virtual Compton Scattering). I will discuss in this presentation the importance of having a multi-reaction approach with other Compton-like, and hard exclusive meson measurements, to go beyond what can be achieve with solely DVCS. I will show projections for current and future experiments for Timelike Compton Scattering, Double Deeply Virtual Compton Scattering, and Vector meson production experiments. I will show projections of the newly achieved accuracy in extracting Compton Form Factors, and emphasize what is new from these reactions in comparison to DVCS.
Jet physics represents a cornerstone in the on-going endeavour to pinpoint the effect of a hot, thermal medium, namely the quark gluon plasma, in QCD dynamics. In this talk, I will revisit our understanding of the jet-medium interaction with a particular emphasis on the interplay between vacuum and in-medium radiation. Further, I will discuss the usefulness of jet substructure observables to probe the perturbative regime of jet evolution and the current challenges on interpreting jet substructure measurements in heavy-ion collisions.
The sPHENIX detector at RHIC is currently under construction and is on schedule for first data in early 2023. At mid-rapidity it consists of a silicon pixel vertexer, a silicon strip detector with single event timing resolution and a compact TPC; as well as an EM calorimeter and a 1.4T BaBar superconducting solenoid sandwiched by an inner and outer hadronic calorimeter.
sPHENIX will allow for state-of-the-art measurements of jets, jet substructure, jet correlations, and heavy flavor jets with kinematic reach overlapping measurements at the LHC due to its acceptance and hybrid streaming/triggered readout that enables full exploitation of the luminosity provided by RHIC.
The talk will discuss sPHENIX readiness for operations, projections of key jet measurements, and the scientific impact of the measurements.
The fast development of quantum technologies over the last decades has offered a glimpse to a future where the quantum properties of multi-particle systems might be more fully understood. So far, quantum computing has seen ample application in areas such as quantum chemistry or condensed matter, but its usage in high-energy physics (HEP) is still in its infancy. In this talk, I will first offer a summary of some recent applications of Quantum Information Science to HEP problems, ranging from ab initio simulations in QFT to computational speed up of jet algorithms. Then, I will discuss in detail a recent proposal to use digital quantum computers to study the evolution of jets in quark gluons plasmas. I will consider the evolution of a single parton, neglecting radiative energy loss and focusing on momentum diffusion. Using the typical approximations found in jet quenching literature, this problem is easily solved and thus it offers a good first step towards studying full jets. Besides the formulation of the problem in terms of operations on the quantum computer, I will also show simulations using IBM's software.
Searching QCD critical point is one of the fundamental goals of heavy-ion collisions. The observed non-monotonic behavior with the colliding energies[1,2] was declared to be related to the critical point of the QCD phase diagram[3,4].
To reveal the critical fluctuations effects on the light-nuclei productions, one should address the problem of scale separation and magnitude separation problems. Specifically, the scale or the magnitude related to the background effects on light-nuclei production are dramatically larger than the ones of critical fluctuations, which hinders the detection of critical signal in light-nuclei individually. In this talk, I will focus on this problem and study the possible effect.
Within the coalescence model, we systematically study how does the background[5] and critical signal[6] play the role in the production of light nuclei. We find that the productions of light-nuclei with different number of constituent nucleons share the same structure up to second-order phase-space cumulants. Accordingly, we construct light-nuclei yield ratio which is directly proportional to the critical correction. The large scales related to light-nuclei are largely cancelled in the ratios and critical correlation length plays an important role. This reveals that the properly constructed yield ratios, not the yield individually, largely free from the scale and magnitude problems. In addition, we also predict a non-trivial behavior of the constructed light-nuclei yield ratios as the imprint the critical fluctuations and could be regarded as one of the candidates to probe the critical point.
[1] H. Liu, D. Zhang, S. He, K.-j. Sun, N. Yu, and X. Luo, Phys. Lett. B 805, 135452 (2020).
[2] D. Zhang (STAR), JPS Conf. Proc. 32, 010069 (2020).
[3] E. Shuryak and J M.Torres-Rincon, Eur.Phys.J.A 56 (2020) 9,241.
[4] K.-j. Sun, F.Li and C.M.Ko, Phys.Lett.B 816 (2021) 136258.
[5] S.Wu, K.Murase, S.Tang and H.Song, 2205.14302.
[6] S.Wu, K.Murase, S.Zhao and H.Song, to appear.
The phase structure of baryonic matter is investigated with focus on the role of fluctuations beyond the mean-field approximation. The prototype test case studied is the chiral nucleon-meson model, with added comments on the chiral quark-meson model. Applications to nuclear matter include the liquid-gas phase transition. Extensions to high baryon densities are performed for both nuclear and neutron matter. The role of vacuum fluctuations is systematically explored. It is pointed out that such fluctuations tend to stabilize the hadronic phase characterized by spontaneously broken chiral symmetry, shifting the chiral restoration transition to very high densities. This stabilization effect is shown to be further enhanced by additional dynamical fluctuations treated with functional renormalisation group methods.
This work has been supported in part by DFG (Project-ID 196253076 - TRR 110) and NSFC as well as the DFG Excellence Cluster ORIGINS.
Understanding how nuclei behave at the extremes of neutron and proton number is critical to developing a predictive theory of nuclei and how they interact. This knowledge, in turn, allows us to elucidate the chemical history of the universe, use nuclei as laboratories to test fundamental symmetries, and develop tools and related technologies that can benefit society. The US Department of Energy's new flagship facility for low energy nuclear physics, the Facility for Rare Isotope Beams (FRIB), began operations this year. In this overview, I will discuss the overarching science goals of FRIB, highlight the unique facility capabilities, and briefly describe the first experiments.
The future Electron-Ion Collider (EIC) in the US – with experimental operations starting in the early 2030s – is poised to be the machine in high-energy nuclear physics to answer longstanding question in hadronic physics. It will be capable of operating at luminosities up to $10^{34}$ cm$^{-2}$s$^{-1}$, and be the only machine able to collide polarized electron and polarized light / nuclear beams up to the highest A. A major component of the EIC physics program is the detection of diffractive final states which can produce particles very close to the beam ($\theta$ < 35 mrad) – the so-called “far-forward” region of the EIC interaction region. Measurement of these diffractive final states requires use of multiple detector sub-systems integrated into the hadron beamline, which provides a challenge for integration with the accelerator magnets and vacuum system. Additionally, the exclusive and diffractive final states measured in the far-forward region can also leverage different machine optics configurations, which provide a tradeoff between detector acceptance and luminosity, and allow for optimal conditions for tagging final state particles in different regions of the far-forward phase space. In addition to the far-forward region, there is also instrumentation integrated in the far-backward (electron-going) region used for tagging events with $Q^{2}$ < 1 GeV$^{2}$, and for monitoring the luminosity. In this talk, I will discuss these far-forward and far-backward detector subsystems in detail, and discuss the various challenges faced in integrating these detectors with the EIC machine.
The Jefferson Lab Eta Factory (JEF) experiment is an upcoming experiment designed to run in Hall D at Jefferson Lab using an upgraded GlueX spectrometer to study various decays of the $\eta$ meson. The GlueX spectrometer consists of a $\sim$2 Tesla solenoid magnet housing a liquid hydrogen target and drift chambers used for tracking charged particles and an array of lead glass blocks (the Forward Calorimeter (FCAL)) downstream of the magnet for detecting neutral particles. The decays of the $\eta$ meson can be used to measure the light quark mass ratio via the $\eta\to\pi^+\pi^-\pi^0$ channel and allow access to higher-order terms in Chiral Perturbation Theory via the $\eta\to\pi^0\gamma\gamma$ channel. The decays can also be used to constrain new charge-conjugation violating/parity conserving (CVPC) reactions and to search for signatures of dark matter. In particular, the $\eta\to\pi^0\gamma\gamma$ channel can be used to search for lepto-phobic dark vector ($B$) bosons in the reaction $\eta\to B\gamma$ ($B\to\pi^0\gamma)$ or dark scalar ($S$) bosons in the reaction $\eta\to\pi^0S$ ($S\to\gamma\gamma$). Studying the rare radiative decay channel $\eta\to\pi^0\gamma\gamma$ requires
replacing the $4\times4\times45$ cm$^3$ lead glass blocks in the inner region of the FCAL with $2\times2\times20$ cm$^3$ lead tungstate crystals, which will provide twice better position and energy resolution. This talk will describe the JEF physics program and the upgrade to the FCAL.
This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Thomas Jefferson National Accelerator Facility (JLab) in Virginia, USA, is home to several experiments studying strange baryons using electro- and photoproduction on a range of different targets. In this presentation we will review recent results with a focus on the CLAS(12) and GlueX experiments. We will also give a short outlook towards future measurements performed with a KLong beam.
With the large datasets on 𝑒+𝑒−annihilation at the 𝐽/𝜓 and 𝜓(3686) resonances collected at the BESIII experiment, multi-dimensional analyses making use of polarization and entanglement can shed new light on the production and decay properties hyperon-antihyperon pairs. In a series of recent studies performed at BESIII, significant transverse polarization of the (anti)hyperons has been observed in 𝐽/𝜓 or 𝜓(3686) to ΛΛ ̄ , ΣΣ ̄ , ΞΞ ̄, and Ω−Ω ̄+ and the spin of Ω− has been determined model independently for the first time. The decay parameters for the most common hadronic weak decay modes were measured, and due to the non-zero polarization, the parameters of hyperon and antihyperon decays could be determined independently of each other for the first time. Comparing the hyperon and antihyperon decay parameters yields precise tests of direct, Δ𝑆 = 1 CP-violation that complement studies performed in the kaon sector.
Among the light baryons, the $J^\pi = \frac{1}{2}^-$ $\Lambda(1405)$ baryon is an important special case by sitting just below the $\bar{K}N$ threshold and decaying almost exclusively to $\Sigma\pi$. It has long been hypothesized to be either a molecular bound state or a continuum resonance, or that it is a simple quark-model resonance, the $P$-wave companion of the $\Lambda(1520)$. In recent years chiral unitary models have suggested$^a$ that there are two isospin zero poles present in this mass region, and that the ``line shape" of the $\Lambda(1405)$ depends to what extent each of the two poles are stimulated in a given reaction. Evidence for this interpretation was reported by the CLAS collaboration$^b$ in elementary photoproduction, albeit with limited statistics. Below the $N\bar{K}$ threshold, the $\Lambda(1405)$ decays to the three $\Sigma\pi$ charge combinations, but the $\Sigma^{0}\pi^{0}$ mode is purely $I=0$, uncontaminated by complications arising from $I=1$ scattering processes contributing to the reaction mechanism in the $\Sigma^{+}\pi^{-}$ and $\Sigma^{-}\pi^{+}$ decays, nor from production and decay of the nearby $\Sigma^{0}(1385)$ hyperon.
The GlueX experiment at Jefferson Lab has been used to study the $\Lambda(1405) \to \Sigma^{0}\pi^{0}$ decay mode with a photon beam in the energy range 6.5 - 11.6 GeV incident on a liquid hydrogen target and using a large acceptance charged particle tracking and electromagnetic calorimeter system. We focus on the preliminary results of $d\sigma/dM_{\Sigma^{0}\pi^{0}}$ in the $-(t-t_{min})$ range 0 - 1.5 GeV$^2$ from analyzing the reaction $\gamma p \to K^{+}\Lambda^*$ using the data collected during the first phase of the GlueX experiment.
Two hypotheses were compared for fitting the line shape of $\Lambda(1405)$ - a single $\Lambda(1405)$ state and two coherent states parameterized with Flatt\'{e} amplitudes. Our preliminary results favor the use of two coherent states to fit the line shape and indicate the $\Lambda(1405)$ is a composite baryon state.
$^a$cf. recent review: M. Mai, U-G, Meissner, Eur. Phys. J. A 51, 30 (2015)
$^b$K. Moriya et al.(CLAS Collaboration), Phys. Rev. C 87, 035206 (2013)
We study for the first time the $p\Sigma^-\to K^-d$ and $K^-d\to p\Sigma^-$ reactions close to threshold and show that they are driven by a triangle mechanism, with the $\Lambda(1405)$, a proton and a neutron as intermediate states, which develops a triangle singularity close to the $\bar{K}d$ threshold. We show that the cross section, well within measurable range, is very sensitive to different models that, while reproducing $\bar{K}N$ observables above threshold, provide different extrapolations of the $\bar{K}N$ amplitudes below threshold. The observables of this reaction will provide new constraints on the theoretical models, leading to more reliable extrapolations of the $\bar{K}N$ amplitudes below threshold and to more accurate predictions of the $\Lambda(1405)$ state of lower mass.
Quantum Chromo Dynamics (QCD) is our current best description of interactions between quarks and gluons and it not only predicts the existence of the well understood mesons (two-quark) and baryons (three-quark) it also predicts exotic Tetra, Penta and Hexaquark states.
Experiments taking place at Thomas Jefferson Lab in Virginia, USA using the upgraded CLAS12 detector system allows a detailed investigation of exotic hadron states. In our experiment electrons accelerated to an energy of 10.6 GeV scatter off either a liquid hydrogen or liquid deuterium target. Various interesting effects can be explored in these reactions, including production of exotic hadrons, such as hybrids, pentaquarks or hexaquarks, the latter being the subject of this research.
This talk will present the analysis of data recently collected at CLAS12, which provides the first search for the ds hexaquark, a particle with quark content uuudds or uuddds with the most promising decay channels expected to be ed→e’K+ds→ e’K+Λn and ed→e’K+ds→ e’K+dK-. The results of the analysis were benchmarked utilizing more conventional reactions. First results on a ds search will be presented, through the lens of polarization of the Lambda. From theory and the analogous d* → pn reaction, we know that a peak in polarization should be seen at the mass of the ds.
Our experimental studies will be confronted with state-of-the-art theoretical calculations on ds branching ratios and partial widths. It will be demonstrated that the expected ds width is well within measuring capabilities of the CLAS12 setup, regardless of the nature of the ds dibaryon (hexaquark or molecular). It will be shown that precise knowledge of the ds mass and width constrains its internal structure.
Electromagnetic polarizabilities are fundamental properties of composite systems such as molecules, atoms, nuclei and hadrons. Polarizabilities measure the 'stiffness' of a system to electromagnetic deformation. Measurements of hadron polarizabilities provide a test of effective field theories, dispersion theories, and lattice calculations. While significant progress has been made in measurements of nucleon polarizabilities, with uncertainties for the proton at the level of 0.4 x 10-4 e fm2, experimental constraints on the charged and neutral pion polarizabilities (CPP and NPP) are much weaker, 2 x 10-4 for the charged pion and no measurement for the neutral pion. The CPP and NPP experiments at GlueX utilize a new technique to measure pion polarizabilities, Primakoff photo-production of charged and neutral pion pairs using linearly polarized 6 GeV photons on a 208Pb target. Details of the experimental setup and preliminary analysis will be presented in the talk. The CPP and NPP experiments are finishing data taking at JLab summer 2022.
Both muon and hadron beams with a energy up to few hundred GeV are available at the M2 beamline of the CERN/SPS. AMBER (Apparatus for Meson and Baryon Experimental Research) is a new fixed-target experiment started in 2021. An ambitious experimental program of AMBER address the various aspects of the so-called Emergence of Hadron Mass mechanism: the charge radii of various hadrons, parton momentum distributions in mesons, as well as the kaon polarizability and the kaon-induced hadron spectroscopy. The first phase of the program incudes: measurements of the proton charge radius in muon-proton scattering to address a long-standing puzzle, measurements of the antiproton production cross section in proton-helium collisions to provide valuable input for the searches of Dark Matter, and pion-induced Drell-Yan and J/psi production measurements to improve knowledge of the meson structure.
Electrons are much cleaner probes of nucleon structures than hadron beams. At the same time the electron scattering at large momentum transfer can be a source of considerable photon radiation, which can significantly distort the inferred nucleon structure if it is not properly accounted for. We present a factorized approach to semi-inclusive deep inelastic scattering, which treats QED and QCD radiation on equal footing and provides a systematically improvable approximation to the extraction of transverse momentum dependent parton distributions. We demonstrate how the QED contributions can be well approximated by collinear factorization, and illustrate the application of the factorized approach to QED radiation in inclusive scattering. For semi-inclusive processes, we show how radiation effects prevent a well-defined "photon-hadron" frame, forcing one to use a two-step process to account for the radiation. We illustrate the utility of the new method by explicit application to the spin-dependent azimuthal asymmetries.
Pion parton distribution functions (PDFs) have a long standing debate in QCD regarding the behavior of the valence quark PDF as the momentum fraction, $x$, approaches 1. Recently the Jefferson Lab Angular Momentum (JAM) collaboration has included both the historical fixed-target Drell-Yan (DY) data and the leading neutron (LN) electroproduction data from HERA in a simultaneous global QCD analysis. Both datasets together allows us to study the pion PDFs across a wide range of momentum fraction. Addressing the large-$x$ behavior, we have also introduced a systematic study of threshold resummation in the DY hard coefficients as well as the inclusion of reduced Ioffe time pseudo-distributions calculated from lattice data. In this talk, I explore these topics as well as potential impacts on pion PDFs from future facilities.
We reinterpret jet clustering as an axis-finding procedure which, along with the proton beam, defines the virtual-photon transverse momentum $q_T$ in deep inelastic scattering (DIS). In this way, we are able to probe the nucleon intrinsic structure using jet axes in a fully inclusive manner, similar to the Drell-Yan process. We present the complete list of azimuthal asymmetries and the associated factorization formulae at leading power for deep-inelastic scattering of a nucleon. The factorization formulae involve both the conventional time-reversal-even (T-even) jet function and the T-odd one, which have access to all transverse-momentum-dependent parton distribution functions (TMD PDFs) at leading twist. Since the factorization holds as long as $q_T \ll Q$, where $Q$ is the photon virtuality, the jet-axis probe into the nucleon structure should be feasible for machines with relatively low energies such as the Electron-Ion Collider in China (EicC). We show that, within the winner-take-all (WTA) axis-finding scheme, the coupling between the T-odd jet function and the quark transversity or the Boer-Mulders function could induce sizable azimuthal asymmetries at the EicC, the EIC and HERA. We also give predictions for the azimuthal asymmetry of back-to-back dijet production in $e^+e^-$ annihilation at Belle and other energies.
In the present work, we have explored the higher twist T-even TMD $h_3$ in the light-front quark-diquark model. Within the same model, we have studied their relations with the leading twist TMDs and also calculated its average transverse momentum.
The PHENIX experiment collected data from a variety of collision species and energies at the Relativistic Heavy Ion Collider (RHIC) through 2016. Analyses of the large amounts of data collected continue to yield intriguing results that further our understanding of QCD from understanding properties of the proton to the hot dense phase of nuclear matter produced in heavy ion collisions known as the quark gluon plasma (QGP). In particular, PHENIX uses measurements of photons, heavy flavor, and jet particles to probe properties of the QGP in 200 GeV Au+Au collisions. To explore the onset of these QGP effects, PHENIX has measured flow, quarkonia, and direct photons in small collision systems. PHENIX also utilizes the polarized proton collisions to study the spin structure of the proton. A selection of recent results, focused on measurements in heavy ion collisions, from the PHENIX collaboration will be highlighted in this talk.
Understanding the high energy limit of Quantum Chromodynamics (QCD) is one of the outstanding goals in nuclear and particle physics. At very high energies, it is conjectured that hadrons and nuclei transform into a universal form of matter known as the Color Glass Condensate (CGC). The CGC is an effective field theory for high-density saturated small-x gluons. This framework has been confronted with experimental data from HERA, RHIC, and the LHC, where hints of gluon saturation have been observed. In this talk, I will review the state of the art of the CGC with an eye toward the Electron-Ion Collider (EIC) era. I will emphasize recent next-to-leading-order computations for a variety of processes, and the potential for the discovery of gluon saturation at the EIC.
Deconfined quarks and gluons are expected to be created in the relativistic heavy-ion collision. According to the coalescence model, yields of exotic hadrons are expected to be strongly affected by their structures [1]. Searching for exotic state particles and studying their properties can extend our understanding of quantum chromodynamics (QCD). The $f_{0}$(980) resonance is an exotic state decaying primarily into $\pi\pi$. Currently the structure and quark content of the $f_{0}$(980) is unknown with several predictions from theory being a $q\overline{q}$ state, a $qq\overline{q}\overline{q}$ state, a $K\overline{K}$ molecule state, or a gluonium state. We report the first $f_{0}$(980) elliptic flow ($v_{2}$) measurement from 200 GeV Au+Au collisions at STAR. The transverse momentum dependence of $v_{2}$ is examined and compared to those of other hadrons (baryons and mesons). The empirical number of constituent quark (NCQ) scaling is used to investigate the constituent quark content of $f_{0}$(980) [2], which may potentially address an important question in QCD. We will report our findings and discuss its implications.
[1] S. Cho, etal. (ExHIC Collaboration), Phys. Rev. Lett. 106, 212001 (2011)
[2] A. Gu, T. Edmonds, J. Zhao, F. Wang, Phys. Rev. C 101, 024908 (2020), arXiv:1902.07152
One of the main goals of ultra-relativistic nuclear collisions is to create a new state of matter called quark-gluon plasma (QGP) and study its properties. Anisotropic flow $v_n$, defined as the correlation of the azimuthal angle of each particle with respect to a common symmetry plane $\Psi_n$, is an ideal probe of QGP's properties. The $v_n$ and $\Psi_n$ represent the magnitude and the phase of a complex flow vector $V_n$, respectively. Azimuthal anisotropies are traditionally measured using 2- and/or multi-particle correlations over a large range in $p_\mathrm{T}$ and $\eta$. However, hydrodynamic calculations show that the event-by-event fluctuations in the initial conditions and the dynamics during the system expansion lead to flow vector fluctuation in $p_\mathrm{T}$ and/or $\eta$ including flow angle and flow magnitude fluctuations.
In this talk, we present the investigations on the $p_{\rm T}$-dependent flow vector fluctuations in Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02\,{\rm TeV}$ generated with A Multi-Phase Transport model (AMPT). New multi-particle correlators can separate the flow angle and magnitude fluctuations and can serve as a tool to study them separately in experiments. Additionally, the flow vector, angle and magnitude fluctuations can significantly improve the understanding of the initial conditions and the dynamic evolution of the created systems in heavy-ion collisions.
The quark-gluon plasma (QGP) is a deconfined state of nuclear matter made of free quarks and gluons, created under high temperature or energy density. Charmonia, bound states of charm and anti-charm quarks, are very special probes of the deconfined medium. $J/\psi$, the vector meson ground state of the charmonium family is abundantly produced at the LHC energies but its production mechanism is still not fully understood, already in elementary proton-proton collisions. In heavy-ion collisions, heavy quarks are produced at the early stages of the collision, therefore they can experience the full collision history, including the QGP phase, providing some insights on the created medium. In particular, $J/\psi$ mesons can experience dissociation inside the QGP as well as recombination, the latter happening at the LHC energies due to the high $c\overline{c}$ production cross section. In addition, the initial geometrical asymmetry of the heavy ion collision and the hydrodynamical aspects of the hot medium can induce a non-zero $J/\psi$ elliptic flow, as they can inherit the flow of the charm quarks through the recombination. Disentangling the prompt and non-prompt $J/\psi$ production, the latter arising from the decays of beauty hadrons, is crucial to understand the different impact of the medium on the bottom and charm quarks. In p--Pb collisions, charmonium measurements are used as reference to study Cold Nuclear Matter effects. Finally, charmonium measurements in high multiplicity pp and p--Pb collisions can bring further insight on heavy quark collectivity in small systems and charmonium production mechanisms via multiple parton interactions.
This talk will present the latest results on $J/\psi$ production at forward and midrapidity in ALICE using Run 2 data. We will present the inclusive, prompt and non-prompt $J/\psi$ production and the inclusive $J/\psi$ elliptic flow measurements in pp, p--Pb and Pb--Pb collisions. Finally, we will discuss the measurements of double $J/\psi$ production in pp collisions, and the $J/\psi$ production as a function of charged particle multiplicity in pp and p--Pb collisions. ALICE results will be compared to results from other experiments and to theoretical models.
The J-PARC is a research complex comprised Material and Life Science Experimental Facility (MLF), Neutrino Experimental Facility and Hadron Experimental Facility (HEF). The HEF is designed as a multi-purpose facility for a variety of particle, hadron and nuclear physics programs. It provides intense secondary beamlines which deliver pions and/or kaons. One of the main topics is hyper-nuclear physics realized with an intense kaon beam. In addition, taking advantage of the three-times more intense pion beam, the interaction between nucleon and hyperon has been investigated. The talk highlights recent activities at the facility and presents near-future plans looking forward.
The new beamline, named as high-momentum beamline has been constructed. It provides primary protons which are directly used for the experiment to measure di-electrons produced in 30 GeV pA reactions. The medium modification of vector mesons is minutely inspected. The commissioning of beamline and the spectrometer was performed in 2021. The detail and status of the experiment will be reported.
The HEF continue to evolve to extend researches and provide new opportunities. The high-momentum beamline will be utilized as a secondary beamline, enable us to start baryon spectroscopies for cascade and charm. The plan of the facility upgrade is also announced and the detail will be presented.
Strangeness Nuclear Physics is a broad field of research that studies hadron processes and nuclear systems containing strangeness, from single- to multi-strangeness systems, and from few-body systems to neutron stars. This talk presents an overview of the progress made in strangeness nuclear physics and related fields over the last few years. It will be seen that, despite the difficult times and challenging circumstances, the strangeness nuclear physics community has kept the field alive, providing many interesting results and achievements which pave the way to face the new challenges ahead.
State-of-the-art simulations of lattice QCD are now being carried out at physical parameters of the theory. Using these simulations one can compute using directly the theory of the strong interactions hadron quantities of interest precisely. Such quantities include charges, form factors, Mellin moments and parton distributions all of which yield rich information on hadron structure.
The High Acceptance Di-Electron Spectrometer (HADES) [1] installed at GSI is a versatile detector, which was originally designed to study medium effects in e+e− production in heavy-ion reactions in the SIS-18 energy range (1-2 GeV/nucleon). Its excellent particle identification capabilities allowed for a systematic investigation of dielectron, strange particles and pion production in proton, deuteron or heavy-ion induced reactions on proton or nucleus. The obtained dilepton spectra measured at various beam energies show important contributions from baryon resonance decays (R → N e+e−) and a strong influence of the
intermediate vector mesons (ρ/ω/φ) in the corresponding time-like electromagnetic form factors [2, 3].
In order to directly access such transitions, HADES has started a dedicated pion-nucleon program using the pion beam line at GSI [4]. For the first time, combined measurements of hadronic and dielectron final states have been performed in π-N reactions in the second resonance region, using polyethylene and carbon targets [5, 6]. While providing new determinations of the baryon-meson couplings, the data allow to investigate the helicity structure of the time like electromagnetic baryon transitions. These results will be presented, together with their confrontation to various versions of the Vector Dominance Model for baryon transitions and to quark-constituent model calculations of time-like electromagnetic transition form factors, emphasizing the role of meson cloud contributions in this kinematical region.
Very recently, the proton-proton reaction at 4.5 GeV was measured by the HADES collaboration in an experiment, using the upgraded HADES detector within the FAIR-Phase0 programme [7]. Prospects for baryon electromagnetic transitions studies in the hyperon sector will therefore also be shortly discussed.
References
[1] G. Agakishiev et al. [HADES], Eur. Phys. J. A 41 (2009), 243-277.
[2] J. Adamczewski-Musch et al. [HADES], Phys. Rev. C 95 (2017) no.6, 065205.
[3] G. Agakishiev et al. [HADES] Eur. Phys. J. A 50 (2014), 82.
[4] J. Adamczewski-Musch et al. [HADES], Eur. Phys. J. A53 (2017) 188.
[5] J. Adamczewski-Musch et al. [HADES], Phys. Rev. C 102 (2020) no.2, 024001.
[6] R. Abou Yassine et al. [HADES], arXiv:2205.15914 [nucl-ex].
[7] J. Adamczewski-Musch et al. [HADES and PANDA], Eur. Phys. J. A 57 (2021) no.4,138.
I will give a brief overview of the state of the art of TMD factorization and of 3D nucleon structure phenomenology, focusing on a personal selection of hot topics. I will then highlight some of the future perspectives in this field.
During two data taking compains in 2011-18 LHCb experiment has collected large samples of beauty and charm hadrons produced in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. These samples are used to study properties and decays of conventional mesons. In this contribution a summary of the LHCb experimental results released in 2022 is presented.
The vast majority of hadrons are not stable with respect to the strong interactions, and are seen as resonant enhancements in the scattering of the lightest stable hadrons. Recent developments have enabled the determination of hadron resonance properties from scattering amplitudes determined from lattice QCD. A summary of the approach will be given, and examples will be presented for heavy-light mesons.
Accessing the hadron spectrum from Quantum ChromoDynamics (QCD) poses several challenges given its non-perturbative nature and the fact that most states couple to multi-particle decay modes. Although challenging, advances in both theoretical and numerical techniques have allowed us to determine few-body systems directly from QCD. A synergistic approach between lattice QCD and scattering theory offers a systematic pathway to numerically compute properties such as the hadron spectrum from first principles. I will present an overview of this program, and discuss developments in determining three-body scattering processes and electroweak transitions of multi-hadron systems. These techniques allow us to push the boundaries of resolving the few-body problem in spectroscopy, and gives us insight into the structure of hadrons as the emergent phenomena of QCD.
We perform a theoretical study of the $D_s^{+}\to \pi^{+}\pi^{+}\pi^{-}\eta$ decay. We look first at the basic $D_s^{+}$ decay at the quark level from external and internal emission. Then hadronize a pair or two pairs of $q\bar{q}$ states to have mesons at the end. Posteriorly the pairs of mesons are allowed to undergo final state interaction, by means of which the $a_0(980)$, $f_0(980)$, $a_1(1260)$, and $b_1(1235)$ resonances are dynamically generated. The $G$-parity is used as a filter of the possible channels, and from those with negative $G$-parity only the ones that can lead to $\pi^{+}\pi^{+}\pi^{-}\eta$ at the final state are kept. Using transition amplitudes from the chiral unitary approach that generates these resonances, and a few free parameters, we obtain a fair reproduction of the six mass distributions reported in BESIII experiment.
We study the $\Omega(2012)$ which was measured in the Belle experiment. We conduct a study of the interaction of the $\bar K \Xi^*$, $\eta \Omega$($s$-wave) and $\bar K \Xi$($d$-wave) channels within a coupled channel unitary approach. We also present a mechanism for $\Omega_c \to \pi^+ \Omega(2012)$ production through an external emission Cabibbo favored weak decay mode, where the $\Omega(2012)$ is dynamically generated from the above interaction. The picture has as a consequence that one can evaluate the direct decay $\Omega_c^0 \to \pi^+K^- \Xi^0$ and the decay $\Omega_c^0 \to \pi^+\bar{K} \Xi^*$, $\pi^+\eta\Omega$ with direct coupling of $\bar{K}\Xi^*$ and $\eta\Omega$ to $K^- \Xi^0$. We find that all data including the Belle experiment on $\Gamma_{\Omega^* \to \pi \bar K \Xi}/ \Gamma_{\Omega^* \to \bar K \Xi}$, are compatible with the molecular picture stemming from meson baryon interaction of these channels. I will give a presentation based on Refs. [1]-[3].
[1] R. Pavao and E. Oset, Eur. Phys. J. C78, 857 (2018).
[2] N. Ikeno, G. Toledo, and E. Oset, Phys. Rev. D 101, 094016 (2020).
[3] N. Ikeno, W. H. Liang, G. Toledo, and E. Oset, arXiv:2204.13396 [hep-ph] (2022).
Classification of tetraquarks states using SU(6) spin-flavor symmetry alongwith SU(3) and SU(2)is done by using Young tableau method. We also have predicted the tetraquark masses and their decay widths by using the extension of Gursey- Radicati mass formula and our results are in very close agreement with the available experimental and theoretical data.
The identification of X(3872) requires a comparison of its properties with those expected for ordinary $c{\bar c}$ states, in particular for $\chi_{c1}^\prime$ which is the candidate ordinary state for the X(3872) identification. I will discuss predictions for observables involving $\chi_{c1}^\prime$ and work out relations with other observables involving ordinary charmonia.
Theretical status of anomalies in semileptonic B decays
We investigate the two-photon transitions of the charmonium system in relativistic dynamics on the light front. The light-front wave functions were obtained from solving the effective Hamiltonian based on light-front holography and one-gluon exchange interaction within the basis light-front quantization approach. We compute the two-photon transition form factors as well as the two-photon decay widths for S- and P-wave charmonia, ηc and χcJ and their excitations.Without introducing any free parameters, our predictions are in good agreement with the recent experimental measurements by BABAR and Belle, shedding light on the relativistic nature of charmonium.
We investigate the cos2𝜙𝑡 azimuthal asymmetry in 𝑒 𝑝→𝑒 𝐽/𝜓 𝐽𝑒𝑡 𝑋, where 𝐽/𝜓-jet
pair is almost back-to-back in the transverse plane, within the framework of the
generalized parton model(GPM). We use non-relativistic QCD(NRQCD) to calculate
the 𝐽/𝜓 production amplitude and incorporate both color singlet(CS) and color
octet(CO) contributions to the asymmetry. We estimate the asymmetry using different
parametrizations of the gluon TMDs in the kinematics that can be accessed at the
future electron-ion collider (EIC) and also investigate the impact of transverse
momentum dependent (TMD) evolution on the asymmetry. We present the contributions
coming from different states to the asymmetry in NRQCD.
In present work we study the production of ground and excited charmonium states in $e^- e^+ \rightarrow \gamma+ \eta_c(nS)/\chi_{cJ}(nP)(J=0,1)$ [1] through leading order (LO) (tree-level) diagrams, which proceed through exchange of a virtual photon that couples to $\gamma$ and $\eta_c/\chi_{cJ}$ through the triangular quark loop diagram, in the framework of $4\times 4$ Bethe-Salpeter equation (BSE), at center of mass energy, $\sqrt{s}=10.6 GeV.$ With use of Covariant Instantaneous Ansatz, we have been able to express the "3D form" of the amplitude, $M_{fi}$ as a linear superposition of terms involving combinations of $++$, and $--$ components of Salpeter wave functions of final hadron, whose general form is relativistically covariant, and is expressible in terms of the form factors [1]. This work is an extension of previous applications of this method to calculate decay widths of E1 and M1 radiative transitions[2] involving various quarkonia. In the present work, the cross sections for these processes with leading order (tree) level diagrams alone at $\sqrt{s}=10.6 GeV.$ provide a sizable contribution, which might be mainly due to the BSE being a fully relativistic approach that incorporates the relativistic effect of quark spins and can also describe internal motion of constituent quarks within the hadron in a relativistically covariant manner. Our results are compared with the recent data of Belle collaboration[3], and other models,
References:
[1] S.Bhatnagar, V.Guleria, arxiv:2206.02229[hep-ph]v2 (to be submitted soon).
[2] V.Guleria,E.Gebrehana, S.Bhatnagar,Phys. Rev. D104, 094045(2021).
[3] S.Jia et al.,(Belle Collaboration), Phys. Rev. D 98, 092015 (2018).
When center-of-mass energy in heavy-ion collisions decreases down $\sqrt{s_\mathrm{NN}}$ of a few GeV, colliding nuclei are not transparent anymore to each other. This leads to increasingly strong baryon stopping in the collision zone, and the formation of baryon-rich matter, where effects due to resonance excitation play an essential role. The goal is to understand the properties of such a matter, including its equation of state and possible phase structure.
This contribution will discuss the physics outcomes from the data collected by HADES, but also by FOPI at SIS18 and in the STAR beam energy scan program at RHIC. When put together, data provide excitation functions of various informative observables like hadron yields, anisotropy, correlations, and fluctuations.
Particularly interesting are observables related to dileptons. Once produced, they decouple from the hadronic medium and leave the interaction zone undisturbed. This makes them a probe of all the stages of the fireball evolution. With lepton identification in mind, HADES is unique in this energy regime in providing high-precision dilepton data, which will be thoroughly examined during this talk.
We consider the experimental data on yields of protons, strange Λ’s, and multistrange baryons (Ξ, Ω), and antibaryons production on nuclear targets, and the experimental ratios of multistrange to strange antibaryon production, at the energy region from SPS up to LHC, and compare them to the results of the Quark-Gluon String Model calculations. In the case of heavy nucleus collisions, the experimental dependence of the Ξ+/Λ, and, in particular, of the Ω+/Λ ratios, on the centrality of the collision, shows a manifest violation of quark combinatorial rules.
The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. For this purpose, we perform a two-dimensional scan of the phase diagram by varying the collisions' energy and system size.
The NA61/SHINE results from a strong interaction measurement program will be presented in this presentation. In particular, the latest results from different reactions p+p, Be+Be, Ar+Sc, and Pb+Pb on charged kaons spectra, charged pions ratios, protons intermittency, flow, and higher-order moments of multiplicity and net-charge fluctuations are planned to be discussed. The results will be compared with worldwide experiments and predictions of various theoretical models, like EPOS, PHSD, UrQMD, etc. Finally, the motivation, NA61/SHINE plans of the measurements after LS2 and LS3 in heavy-ion collisions at the Super Proton Synchrotron energies will be shown.
The pion-nucleus reaction is an important source of information about hadronic matter. At incident momenta below 2 GeV/c, it gives access in a very unique way to the properties of baryonic resonances in the nuclear medium. While the region of the Δ(1232) resonance, corresponding to incident pion beam momenta of about 300 MeV/c, was studied in detail in the past, only very scarce measurements were provided at higher energies, e.g. in the second resonance region (N(1440), N(1520), N(1535),..). Such information is needed in the context of dense hadronic matter studies for the description of heavy-ion reactions at a few GeV, where pion-nucleus dynamics play a crucial role. More general, measurements of proton and pion differential spectra are needed to validate transport models or hadronic cascades used in GEANT4 for various applications involving pion detection. This talk will focus on the analysis of π⁻+C reactions performed with HADES [1], using the GSI pion beam at an incident pion momentum of 0.7 GeV/c. Pion and proton differential spectra measured in various exit channel topologies (inclusive, pπ⁻, pπ⁺, pp, pπ⁺π⁻,…, ππpp) are compared to predictions of the INCL++ cascade [2] and of transport models (SMASH [3,4], rQMD [5], GIBUU [6],…). The results test selectively the capacity of the models to describe the various mechanisms (quasi-elastic scattering, multipion production, re-scattering and pion absorption). The sensitivity of the data measured in the quasi-elastic channel to short range correlations is also investigated.
[1] G. Agakishiev et al. (HADES collaboration), Eur. Phys. J. A41, 243-277 (2009).
[2] S. Leray et al. J. Phys. Conf. Series 420 (2013) 012065.
[3] J. Weil et al., Phys. Rev., C 94, 054905 (2016).
[4] H. Petersen, Nuclear Physics A, 1 (2018).
[5] H. Sorge, Phys. Rev. C 52, 3291 (1995).
[6] J. Weil et al., Eur. Phys. J., A 48, 111 (2012).
Production of strange quarks in relativistic heavy-ion collisions is not only used as a signature of QGP formation but also as a diagnostic tool. Strange quarks and antiquarks are produced via strong interactions in the QGP medium and are not present in ordinary matter. The reason is that they promptly undergo decay via weak interactions as soon as they are produced. Additionally, the mass of strange quarks, anti quarks, is below and close to the temperature at which protons, neutrons and other hadrons turn into quarks. Hence, these strange quarks, antiquarks are sensitive to the conditions, structure and dynamics of the deconfined state of matter. It can be said that the deconfined state is reached if there is an abundance of strange quarks. In this poster, I will present the comparison between the invariant mass and yield of different strange particles(Λ, Σ, Ω) at different centralities for the events simulated using AMPT and UrQMD model.
Thanks to the recent development of lattice simulation techniques, numerical simulations on an anisotropic system, where the temporal and z directions are compactified while the remaining x and y directions are left infinitely large, have become possible. Such system is understood as an extension of finite-temperature one where only the temporal direction is compactified; namely, the anisotropic system can be regarded as a novel extreme condition of QCD. In this talk, I investigate the phase structures of pure Yang-Mills theory by means of an effective model of Polyakov loops on the anisotropic system, and demonstrate the usefulness of focusing on the novel system comparing to the recent lattice results.
The measurement of the production, the lifetime and the binding energy of the hypertriton with the ALICE detector at the LHC is presented to address some of the key open questions of hypernuclear and particle physics.
The hypertriton is a bound state of a proton (p), a neutron (n) and a Λ and it is characterized by a very low binding energy and a large wave function. It is still unclear how such a fragile object can survive the extreme environment created in ultrarelativistic heavy-ion collisions and the measurement of the production yields in Pb-Pb collisions can shed light on the production mechanism of such a system.
The study of the hypertriton also provides insights into the strong interaction between the lambda and ordinary nucleons and when studied in small colliding systems, like pp and p-Pb collisions, the hypertriton can give useful constraints for the nucleosynthesis models.
Thanks to the very large dataset collected so far in pp, p–Pb and Pb–Pb collisions, the ALICE collaboration has performed systematic and precise measurements of the hypertriton production, lifetime and binding energy, thus also contributing to solving the longstanding hypertriton lifetime puzzle.
In this contribution, an overview of those results will be presented and compared with the existing theoretical predictions and the available experimental data.
The hyperon-nucleon (Y-N) interaction is an important ingredient in the description of the equation-of-state of high-baryon-density matter. Light hypernuclei ($A=3, 4$), being simple Y-N bound states, are cornerstones of our understanding of the Y-N interaction. Precise measurements of the lifetimes and binding energies of light hypernuclei are of particular interest.
Light hypernuclei are expected to be abundantly produced in intermediate to low energy heavy-ion collisions due to the high baryon density. As a result, the STAR Beam Energy Scan Phase II program, spanning an energy range of $\sqrt{s_{\rm{NN}}}=3.0-27.0$ GeV, is particularly suited for hypernuclei studies. In this talk, recent results on the lifetimes of ${}^{3}_{\Lambda}$H, ${}^{4}_{\Lambda}$H, ${}^{4}_{\Lambda}$He measured in $\sqrt{s_{\rm{NN}}}=3.0$ and $7.2$ GeV Au+Au collisions will be presented. The binding energies of ${}^{4}_{\Lambda}$H, ${}^{4}_{\Lambda}$He measured in $\sqrt{s_{\rm{NN}}}=3.0$ GeV Au+Au collisions will also be presented. These results will be compared to previous measurements and theoretical calculations, and the physics implications will be discussed.
We report on our recent leading order pionless effective field theory (LO pionless EFT) studies [1,2,3,4,5] of light single- and double-Lambda hypernuclei. These systems are within the focus of current experimental interest since their spectra provide strong constraints in a study of the 2- and 3-body interaction between $\Lambda$ hyperons and nucleons. Application of LO pionless EFT, fitted to available low-energy data, reveals excited state of hypertriton ${\rm ^3_\Lambda H^*}~(J^\pi=3/2^+)$ in a form of a virtual state and predicts possible broad $\Lambda nn~(J^\pi =1/2^+)$ resonance [2,3] with the resonance energy strongly dependent on the size of $\Lambda N$ scattering length. Considering $\Lambda N$ charge symmetry breaking (CSB) and partially conserved baryon-baryon SU(3) flavor symmetry we deduce from the experimental CSB in $\rm ^4_\Lambda H− ^4_\Lambda He$ hypernuclei in-medium $\Lambda$ isospin $I=1$ admixture amplitude [5]. Our result is in agreement with the free-space value ≈1.5% inferred by Dalitz and von Hippel [6] and recent QCD+QED lattice calculations [7]. Extending LO pionless EFT to the double-$\Lambda$ sector we firmly predict bound ${\rm ^5_{\Lambda \Lambda} H~/~^5_{\Lambda \Lambda} He }~(J^\pi = 1/2^+)$ isospin doublet, while four-body ${\rm ^4_{\Lambda \Lambda} H }~(J^\pi =1^+)$ hypernucleus is found on the verge of binding, strongly dependent on the strength of $\Lambda \Lambda$ interaction [1].
References
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Direct ΛN scattering data is extremely important and needed based on the newly confirmed Charge-Symmetry-Breaking (CSB) at a level of ~230 keV from the binding energy difference observed between ground states of $^4_Λ$He and $^4_Λ$H. Especially, the Λn data does not exist at all, thus the properties of Λn interaction has been assumed to be identical to that of Λp interaction. The resonance of Λnn system, if it does exist, may provide a unique and the only experimental data that can be used to determine the unknown properties of Λn interaction [1].
Because the $^3$H(e, e’K$^+$)(Λnn) reaction is unique for studying the possible neutral Ynn systems, a mass spectroscopy experiment (E12-17-003) with a pair of nearly identical high resolution spectrometers and a tritium target was performed in Hall A at Jefferson Lab. Although the experimental condition with the existing apparatus was not optimized for production of hypernuclei, enhancements, which may correspond to a possible Λnn resonance and a pair of ΣNN states, were observed with an energy resolution of about 1.21 MeV (σ). Since the statistics is low, definitive identifications cannot be made. However, the result is definitely interesting and an optimized experiment for further investigation with much improved statistics is needed.
In addition, although bound A = 3 [2, 3] and 4 Σ-hypernuclei have been predicted, only an A = 4 Σ-hypernucleus ($^4_Σ$He) was found [4], utilizing the (K$^-$, π$^-$) reaction on a $^4$He target. The possible bound ΣNN state is likely a Σ$^0$nn state, although this has to be confirmed by future experiments.
Reference
We investigate 𝑆=−1 and −2 hypernuclei with 𝐴=4−7 employing the Jacobi-NCSM approach [1] and in combination with baryon-baryon (BB) interactions derived within the frame work of chiral effective field theory. The employed BB interactions are softened using the so-called similarity renormalization group (SRG) [2] in order to speed up the convergence. Such a SRG evolution is only approximately unitary when the SRG induced higher-body forces are omitted. Impact of the SRG evolution and of the two almost phase-equivalent YN NLO13 [3] and NLO19 [4] potentials on the $\Lambda$ separation energies of 𝐴=4−7 hypernuclei is thoroughly studied [5]. Finally, we report our recent results for $\Xi$ hypernuclei based on the chiral NLO $\Xi N$ potentials [6]. We found three shallow bound states for the $NNN \Xi$ system while the $^5_{\Xi}\mathrm{H}$ and $^7_{\Xi}\mathrm{H}$ are more tightly bound [7].
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Near-threshold charmonium photoproduction opens the door for studying the gluonic properties of the proton: gluonic GPDs, anomalous contribution to the mass of the proton, gravitational form factors, and the mass radius of the proton. However, such an ambitious program requires precise measurements to validate the theoretical assumptions that relate the experimental results to the above quantities. The first total cross-section measurements of near-threshold exclusive $J/\psi $ photoproduction ($\gamma p \rightarrow J/\psi p$) [1] by the GlueX collaboration sparked remarkable theoretical interest, however had limited statistics. We will report new total cross-section results based on more than a four-fold increase in statistics. Even more, due to the full acceptance of the GlueX experiment for this reaction, we will present first measurements of the differential cross-sections over the whole near-threshold kinematic region. Such measurements enable more general quantitative conclusions about the reaction mechanism, when compared to the theoretical calculations that cover a wide range of methods and reaction channels, from gluon exchange to open-charm intermediate states. Prospects of future $J/\psi $ measurements at Jefferson Lab will be discussed, as well.
[1] A. Ali et al. (GlueX collaboration), Phys. Rev. Lett. 123, 072001 (2019).
$J/\psi$ photo-production near threshold provides a unique window into the non-perturbative structure of the gluonic fields of the nucleon, enabling access to information regarding the origin of its mass and mass radius. In the Jefferson Lab E12-16-007 experiment, we measured the two-dimensional $J/\psi$ photo-production cross-section as a function of photon energy $E_{\gamma}$ and momentum transfer $t$ near-threshold. The E12-16-007 experiment was conducted in the experimental Hall C using a high-intensity bremsstrahlung photon beam generated by a 10.6 GeV incident electron beam traversing a copper radiator upstream of a liquid hydrogen target. We will present new results on the two-dimensional $J/\psi$ photo-production cross-section measurement in photon energy $E_{\gamma}$ and $t$, and their impact on our knowledge of the proton mass radius and the relative quantum anomalous energy contribution to its mass.
The conventional picture of the proton is based on three “valence” quarks—two “up” and one “down”. This picture has done a remarkable job of describing many properties of the proton. However, thanks to the richness of QCD, the proton is a much more complicated object. In addition to the valence quarks, the proton contains a “sea” of quark-antiquark pairs and gluons that bind the system together. Using the Drell-Yan process, a remarkable asymmetry has been observed in the difference of anti-down to anti-up quarks in the proton. This asymmetry cannot simply be generated through perturbative QCD, but rather indicates an underlying and fundamental antiquark component in the proton. This talk will present the latest results from the SeaQuest experiment on the flavor asymmetry in the proton sea, and compare these results with previous measurements, phenomenological parton distributions fits, and models of the proton.
The explicit sea quark distribution functions of proton have been calculated in the
chiral constituent quark model which has implications of chiral symmetry breaking and SU(3) symmetry breaking. The results have been discussed in detail for the sea quark asymmetries and the Gottfried integral in light of the latest SeaQuest data.
I discuss the scope and naturalness of the proton mass decomposition (or sum rule) published in PRL74, 1071 (1995), focusing particularly on its interpretation and the quantum anomalous energy contribution. I stress the importance of measuring the quantum anomalous energy through experiments. I will also discuss the mass radius and relation to the threshold J/psi production on the proton.
Heavy quarkonium production of high transverse momentum ($p_T$) in hadronic collisions can be pursued in the QCD factorization formalism with heavy quarkonium fragmentation functions (FFs), which carry rich information on how a physically observed quarkonium was emerged from quarks and gluons produced in high energy scattering. The scale evolution of quarkonium FFs enables us to resum logarithmically enhanced corrections to the production cross sections. In [arXiv:2108.00305], we demonstrated that the QCD factorization approach at leading-power in $1/p_T$ with single parton FFs describes LHC data on the differential cross-section for $J/\psi$ production in hadronic collisions at $p_T$ much larger than heavy quark mass scale. When $p_T$ decreases, the subleading power contribution with double parton FFs at twist-4 becomes more significant than the leading power contribution. In this talk, we will demonstrate how QCD factorization approach including both leading power and next-to-leading power contributions can describe the transverse momentum distribution of J/psi production at both Tevatron and the LHC, emphasizing the important role of the new subleading power contributions in hadronic quarkonium production and the matching to the low $p_T$ region.
Heavy quarkonium production is considered as useful tools to study perturbative and nonperturbative aspects of QCD. For this, it is essential to understand the mechanism of quarkonium production from QCD theory, which remains elusive to this day. In this talk, we review the current status of theoretical approaches and recent progresses in our understanding of heavy quarkonium production based on nonrelativistic effective field theories.
Based on the potential nonrelativistic QCD formalism, we compute the nonrelativistic QCD long-distance matrix elements (LDMEs) for inclusive production of S-wave heavy quarkonia. This greatly reduces the number of nonperturbative unknowns and brings in a substantial enhancement in the predictive power of the nonrelativistic QCD factorization formalism. We obtain improved determinations of the LDMEs and find cross sections and polarizations of J/ψ, ψ(2S), and excited Υ states that agree well with LHC data. Our results may have important implications in pinning down the heavy quarkonium production mechanism.
We present the next-to-leading order (NLO) calculation of associated hadroproduction of $J/\psi$ plus $W$ or $Z$ bosons within the factorization framework of nonrelativistic QCD (NRQCD). We compare to ATLAS data using various sets of nonperturbative long distance matrix elements (LDMEs) as input. Our results thereby open up a new angle in the ongoing quest to understand whether the LDMEs are universal or not. We give an overview of how these NLO universality tests now unfold, after the inclusion of our new results.
We present the construction of a simple-functional form light-front wavefunctions (LFWFs) of charmonium and bottomonium states on a small-sized basis function representation. In this work, we modeled the LFWFs for four charmonium states and three bottomonium states, $\eta_c$, $J/\psi$, $\psi'$, and $\psi(3770)$, $\eta_b$, $\Upsilon$, $\Upsilon(2s)$, as superpositions of orthonormal basis functions.The basis functions are eigenfunctions of an effective Hamiltonian, which has a longitudinal confining potential in addition to the transverse confining potential from light-front holographic QCD. We employ the experimental measurements of heavy quarkonium decay widths as well as input from NRQCD to determine the basis function parameters and superposition coefficients.
We study the features of those heavy quarkonium states using the obtained wavefunctions, including charge radii and parton distribution functions. Additionally, we use the vector meson LFWF to calculate the meson production in diffractive deep inelastic scattering and ultra-peripheral heavy-ion collisions at LHC, and the $\eta_c$, $\eta_b$ LFWF to calculate its diphoton transition form factor. Both results show agreement with experiments.
In this talk we present our results on production of heavy quarkonia pairs in the kinematics of future electron-proton colliders, like EIC, LHeC and FCC-he, and in ultraperipheral collisions at LHC. We analyzed in detail the mechanism which gives the dominant contribution in the leading order in strong coupling $\alpha_s$, both for the hidden-flavour quarkonia pairs and for the double heavy flavour $B_c$-mesons. For the hidden flavour quarkonia pairs, the suggested mechanism leads to production of quarkonia with opposite $C$-parity. The $B_c$-mesons are always produced as oppositely charged $B_c^+ B_c^-$ pairs. In all cases the quarkonia are produced predominantly with relatively small and oppositely directed transverse momenta. Using the Color Glass Condensate (CGC/Sat) approach, we estimated numerically the cross-section of this mechanism for different quarkonia states in the kinematics of existing and future photoproduction experiments.
This presentation is partially based on materials of our recent publication in Phys. Rev. D 105 (2022) 7, 076022 [arXiv:2202.03288].
Finding the experimental signatures of the local $CP$ violation in the strong interaction is one of the major interests in high-energy physics. Chiral Magnetic Effect (CME) is predicted to occur in the heavy-ion collisions. Although some non-zero results of CME sensitive observables have been obtained at both RHIC and LHC energies in the past decades, search for conclusive evidence of CME is still ongoing, which requires careful consideration of the charge-dependent backgrounds.
Recently, the STAR experiment has reported the latest studies$^{1,2}$ at ${\sqrt{s_{_{\rm NN}}}= 200}$ GeV with two isobaric collision systems, $^{96}_{44}$Ru + $^{96}_{44}$Ru and $^{96}_{40}$Zr + $^{96}_{40}$Zr. A blind analysis has been applied to minimize the possible unconscious bias. In this talk, we will present the findings from the isobar blind analysis. Some future outlooks will be briefly discussed.
[1] J. Adam, et al. STAR Collaboration, Methods for a blind analysis of isobar data collected by the STAR collaboration. Nuclear Science and Techniques, 32, 48 (2021)
[2] J. Adam, et al. STAR Collaboration, Search for the Chiral Magnetic Effect with Isobar Collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV by the STAR Collaboration at RHIC, Physical Review
C, 105, 014901 (2021).
In 2023, the sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) will begin measuring a suite of unique jet and heavy flavor observables with unprecedented statistics and kinematic reach at the RHIC energies using combined EM and hadronic calorimeters and high precision tracking.
The experiment incorporates full azimuth vertexing, tracking, and a complete set of electromagnetic and hadronic calorimetry for electron identification enabling detailed studies of the three Upsilon States, Y(1S), Y(2S) and Y(3S). Because of the different binding energies, bottomonium mesons are particularly useful probes to understand the thermal properties of quark-gluon plasma. sPHENIX will provide high statistics measurements of the separated three Upsilon states over a broad momentum range for the first time at RHIC. A MAPS-based vertex detector upgrade to sPHENIX, the MVTX, will provide a precise determination of the impact parameter of tracks relative to the primary vertex in high multiplicity heavy-ion collisions and polarized proton-proton/proton-nuclei collisions. It will enable precision measurements of open heavy-flavor observables, covering an unexplored kinematic region at RHIC. This talk will describe the current projections for the sPHENIX open and closed heavy flavor measurements in hot and cold nuclear matter and discuss their potential scientific impact.
We study the evolution of the doubly charmed state $T_{cc}^+$ in a hot hadron gas produced in the late stage of heavy-ion collisions. We use effective Lagrangians to calculate the thermally averaged cross sections of $T_{cc}^+$ production in reactions such as $ D^{(*)} D^{(*)} \rightarrow T_{cc}^+ \pi, T_{cc}^+ \rho $ and its absorption in the corresponding inverse processes. We then solve the rate equation to follow the time evolution of the $T_{cc}^+$ multiplicity, and determine how it is affected by the considered reactions during the expansion of the hadronic matter. We compare the evolution of the $T_{cc}^+$ abundance treated as a hadronic $S$-wave molecule and as a tetraquark state. Our results show that the tetraquark yield increases by a factor of about 2 at freeze-out, but it is still one order of magnitude smaller than the final yield of molecules formed from hadron coalescence. Also, the results indicate that $N_{T_{cc}}$ is more affected by interactions with hadronic medium than $ N_{X(3872)} $ in similar conditions. We also show that yields depend very weakly on the system size, represented by $\mathcal{N} = \left[ d N_{ch} / d \eta (\eta < 0.5)\right]^{1/3}$.
We investigate the phase structure and thermodynamic properties of
the Polyakov loop-extended chiral quark mean-field model at different val-
ues of temperature and density. We explore the effect of finite volume and
magnetic field on phase transition from confined hadronic state to decon-
fined quarks. A shift of phase boundary to higher values of quark chemical
potential ($μ_q$) and temperature (T) have been observed for decreasing val-
ues of system volume and an opposite shift to lower temperature and quark
chemical potential for increasing magnetic field. The phase diagram and
critical temperature is modified in presence of magnetic field and finite
size and hence these play a significant role in identifying the transition
temperature more precisely.
The midrapidity transverse momentum (pt) distributions of the charged pions and kaons, protons and antiprotons, measured by ALICE Collaboration at nine centrality groups of Xe+Xe collisions at (snn)1/2=5.44 TeV, have been described quite well using simultaneous (combined) minimum χ2 fits with the simple (non-consistent) as well as thermodynamically consistent Tsallis function with included transverse flow. The parameters T0, 〈β_t 〉, and q extracted in Xe+Xe collisions at (snn)1/2=5.44 TeV using both consistent and non-consistent Tsallis function with included transverse flow have demonstrated the similar dependencies on collision centrality (<Npart>). The obtained non-extensivity parameter q values decrease systematically for all studied particle species with increasing Xe+Xe collision centrality, suggesting an increase in degree of system thermalization with increasing centrality of heavy-ion collisions. The extracted average transverse flow velocity has demonstrated significantly different growth rates in regions <Npart> < 44±5 and <Npart> > 44±5, and parameter T0 has stayed constant within uncertainties in <Npart> > 44±5 range in Xe+Xe collisions at (snn)1/2=5.44 TeV. It is argued that <Npart> 44±5 (<dNch/d> 158±20) could be a threshold border value for a crossover transition from a dense hadronic state to the QGP phase (or mixed phase of QGP and hadrons) in Xe+Xe collisions at (snn)1/2=5.44 TeV. The results obtained in present work for high-energy Xe+Xe collisions have been compared with those for high-energy Pb+Pb collisions at the LHC. Depletion (enhancement) of (p+p ̅)/(π^++π^-) ratio at low pt (intermediate pt) has been observed in present work in Xe+Xe collisions at (snn)1/2=5.44 TeV, which is consistent with the similar results of ALICE Collaboration obtained recently in high-energy Xe+Xe and Pb+Pb collisions at the LHC. Analyzing and reflecting the extracted 〈β_t 〉 versus <Npart> and (p+p ̅)/(π^++π^-) versus <dNch/d> dependencies, we have verified that the depletion (enhancement) of baryon-to-meson ratio at low pt (intermediate pt) values with increasing <dNch/d>, observed in high-energy Xe+Xe and Pb+Pb collisions at the LHC, is due to radial flow effects.
The main motivation is to understand anisotropic flow in deformed collision systems. Here, we will discuss elliptic flow and other higher order flow coefficients (n$\le$4). These coefficients carry essential information about the dynamics of the created medium. The study of anisotropic flow coefficients v n in Xe-Xe collisions at 5.44 TeV under Monte Carlo HYDJET++ model (HYDrodynamics plus JETs) framework is presented. Anisotropic flow of charged hadrons have strong transverse momentum and centrality dependence. Strong centrality dependent correlation is observed between the flow harmonics ($v_{2},v_{3},v_{4}$). HYDJET++ model predicts a linear positive correlation in central collisions while boomerang like correlation structure exists in peripheral collisions as found in ALICE experiment. We find a strong dependence of the above observables on the geometry of collision. Hydrodynamical models predict a 10% increase in elliptic flow ($v_{2}$) for deformed Xe nucleus compared to the spherical Xe-nucleus in central collisions. Thus, it will be an interesting work to visualise correlations between these anisotropic flow coefficients in the scenario of deformed collision systems.
In this talk, I will give a broad overview of the production and detection of dark matter in high-intensity experiments. The dark matter and dark sector candidates include dark scalar, dark photon, millicharged particles, dark neutrino, and dipole-portal heavy neutral leptons in existing and future experiments like MiniBooNE, MicroBooNE, DUNE, SBN, NA62, and SHiP. I also discuss similar signatures in Super/Hyper-K, IceCube, and JUNO.
This talk is based on many references, including but not limited to
1. https://arxiv.org/abs/1706.00424 (dark scalar)
2. https://arxiv.org/abs/1908.07525 (dark photon & inelastic dark matter)
3. https://arxiv.org/abs/1806.03310 (millicharged particles)
4. https://arxiv.org/abs/1803.03262 (dipole portal heavy neutral leptons)
The Positronium system, a bound state of an electron and a positron, is
suitable for testing the predictions of quantum electrodynamics (QED), since its
properties can be perturbatively calculated to high accuracy and is not affected
by finite size or QCD effects at the current experimental precision level. The
Ps triple state, the ortho-Positronium (o-Ps), which mainly decays to three
photons, is a well suited system to perform searches of new physics.
In particular, we propose to study the lifetime of the o-Ps state in search of a
new type of matter, the so-called Alice or Mirror Matter (MM). This new mat-
ter was originally proposed to restore parity violation in weak interactions, by
introducing a new hidden mirror sector where parity is violated in the opposite
way. These mirror partners would interact with Standard Model (SM) particles
mainly via gravitation, making them suitable candidates for Dark Matter.
In the o-Ps system, the photons from the decay would oscillate into their
mirror partners, leaving no signal in the detector. By performing a high precision
measurement of the o-Ps lifetime, the accuracy of the present QED calculations
can be tested. A discrepancy with the expectation from theory could indicate
the presence of Physics Beyond the SM, i.e. a signal for MM.
The search is conducted with the novel Positron-Electron Tomography (PET)
scanner at the Jagiellonian University. The J-PET is a high acceptance multi-
purpose detector optimized for the detection of photons from positron-electron
annihilation and can be used in a broad scope of interdisciplinary investigation,
e.g. medical imaging, fundamental symmetry test and quantum entanglement
studies with o-Ps, etc.
The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment searching for 0νββ decay that has been able to reach the one-tonne mass scale. The detector, located at the LNGS in Italy, consists of an array of 988 TeO2 crystals arranged in a compact cylindrical structure of 19 towers. CUORE began its first physics data run in 2017 at a base temperature of about 10 mK and in April 2021 released its 3rd result of the search for 0νββ, corresponding to a tonne-year of TeO2 exposure. This is the largest amount of data ever acquired with a solid state detector and the most sensitive measurement of 0νββ decay in 130Te ever conducted, with a median exclusion sensitivity of 2.8×10^25 yr. We find no evidence of 0νββ decay and set a lower bound of 2.2 ×10^25 yr at a 90% credibility interval on the 130Te half-life for this process. In this talk, we present the current status of CUORE search for 0νββ with the updated statistics of one tonne-yr. We finally give an update of the CUORE background model and the measurement of the 130Te 2νββ decay half-life, study performed using an exposure of 300.7 kg⋅yr.
We explore the sensitivity of the parity-violating electron scattering (PVES) asymmetry in both elastic and deep-inelastic scattering to the properties of a dark photon. Given advances in experimental capabilities in recent years, there are interesting regions of parameter space where PVES offers the chance to discover
new physics in the near future. There are also cases where the existence of a dark photon could significantly alter our understanding of the structure of atomic nuclei and neutron stars as well as parton distribution functions.
The proton charge radius is one of the important quantities in physics. For the past seventy years it has been measured through elastic electron-proton scattering and ordinary hydrogen spectroscopy methods. Over the years, results from both methods generally agreed with each other within their experimental uncertainties. Unexpectedly, in 2010 (and 2013) two experiments from newly developed muonic hydrogen atomic spectroscopy method reported results up to six standard deviations smaller values than the accepted average from all previous experiments performed on ordinary hydrogen. This discrepancy triggered the well-known proton radius puzzle in hadronic physics. This talk will discuss the first magnetic-spectrometer-free electron-proton scattering experiment (PRad), performed at Jefferson Lab in 2016, emphasizing its methods and results. The current status of the planned second experiment (PRad-II) will also be presented and discussed.
The MUon Scattering Experiment (MUSE), which takes place at the PiM1 beamline of the Paul Scherrer Institut (PSI), aims to simultaneously measure elastic ep and μp scattering in order to determine the proton charge radius. However with the beamline and kinematics available to the experiment, MUSE has a broader physics reach than extracting the proton radius. As the experiment has access to both positively and negatively charged leptons, a precise two photon exchange measurement can be performed for both electrons and muons in the 0.002 < Q^2 < 0.08 (GeV/c)^2 and 0.26 < ε < 0.94 regime. The experiment has both a LH_2 target and a carbon target, allowing for a variety of precise cross section measurements. With access to π^± in the beam it is also possible to measure absolute and relative elastic pion cross sections to high precision with the MUSE detector. In this talk the physics reach of MUSE and projected uncertainties for the measurements will be discussed.
This talk will discuss upcoming tagged deep inelastic scattering (TDIS) measurements in Hall A of Jefferson Lab, which will probe the elusive mesonic content of the nucleon. The TDIS experiment will measure low momentum recoiling (and spectator) hadrons in coincidence with deep inelastically scattered electrons from hydrogen (and deuterium) targets. The recently installed Hall A Super Bigbite Spectrometer, a large acceptance detector package, will be used to detect the electrons. For the hadron detection, a novel, high-rate capable, multiple time projection chamber (mTPC) is being developed. Through use of the mTPC, a tagging technique will enhance deep inelastic scattering from partons in the meson cloud and provide access to the pion and kaon structure functions in the valence regime. An overview of the measurement program will be given.
I’ll discuss the role of the triangle anomaly in polarized deep inelastic scattering (DIS) employing a worldline formalism, which is a powerful framework for the computation of perturbative multi-leg Feynman diagrams. I’ll demonstrate that structure function $g_1(x_B,Q^2)$ measured in polarized DIS is dominated by the triangle anomaly in both Bjorken ($Q^2\rightarrow \infty)$ and Regge ($x_B\rightarrow 0$) asymptotics. I’ll show that the infrared pole of the anomaly appears in both limits. The cancellation of this pole involves a subtle interplay of perturbative and nonperturbative physics that is deeply related to the $U_A(1)$ problem in QCD. In particular I will discuss the fundamental role played in this cancellation by a Wess-Zumino-Witten term that couples the topological charge density to a massless isosinglet pseudoscalar field. I’ll demonstrate the fundamental role played by this contribution both in topological mass generation of the $\eta^\prime$ and in the cancellation of the infrared pole arising from the triangle anomaly in the proton's helicity $\Sigma(Q^2)$. I will introduce an axion-like effective action for the $g_1$ structure function at small $x_B$ that follows from the cancellation of the infrared pole in the matrix element of the anomaly, which describes the interplay between gluon saturation and the topology of the QCD vacuum. Such topological transitions can be measured in polarized DIS at a future Electron-Ion Collider.
A brief overview of the experimental evidence for the non-zero intrinsic charm (IC) contribution to the proton PDF is presented.
The effect of intrinsic heavy quarks in the production of prompt photons or $Z$ bosons accompanied by c and b jets in pp collisions
at the LHC is investigated. Our estimations of constraints on the intrinsic charm content of the proton from LHC data on the
associated production of prompt photons in pp collisions are presented. Then they are compared with similar estimations of NNPDF group.
The LHCb data on the $Z$ boson production accompanied by $c$ jet obtained recently are discussed. They show a sizable enhancement in the
rapidity distribution of $Z$ bosons in the forward kinematical region, which could be interpreted as a signal of the intrinsic charm in proton with
a probability above 1\%, which does not contradict with our estimations of its upper limit.
Including the intrinsic charm component in proton we also predict a significant enhancement in the distribution of charm
jets as a function of $\Delta y=|y_Z - y_c|,$ where $y_Z$ and $y_c$ are the rapidities of the Z-boson and the charm jet, respectively.
Moreover, it is shown that the charm jet production in pp collisions increases significantly at the Feynman variable
$x_F > 0.2$, when the IC component in the proton PDF is taken into account.
We also highlight tests of the $c(x) $ vs. $\bar c(x)$ intrinsic charm asymmetry predicted by LGTH. This $c-{\bar c}$ asymmetry leads to
the asymmetry of $D^+$ and $D^-$ mesons produced in pp collision. The corresponding predictions are presented.
Generation of mass within the Standard Model is typically attributed to the Higgs boson. Yet, alone, the Higgs can only explain a few percent of the proton mass. The remainder must be produced by another source. The answer lies in nonlinear, nonperturbative phenomena within the gauge sector of quantum chromodynamics; in fact, at the most fundamental level, in the emergence of a mass-scale for gluons. This presentation will sketch how gluons acquire mass, describe the manner through which this mass enters the matter sector, and highlight some of the observable impacts of emergent mass on hadron form factors and structure functions.
This presentation will focus on recent advances in understanding the internal structure of baryons and their low-lying excitations. The results are founded on the first-principles approach of Lattice QCD, complemented by Hamiltonian effective field theory (HEFT), a nonperturbative extension of effective field theory incorporating the Luscher formalism.
We'll commence with the low-lying odd-parity nucleon resonances where a new parity-expanded variational analysis enables the first quantitative examination of the electromagnetic form factors of the N(1535) and N(1650) in lattice QCD.
The results lead to a consideration of the even-parity Roper resonance and its isospin-3/2 Delta-resonance partner. Lattice QCD calculations indicate the first radial excitation of the nucleon lies at 1900 MeV, well above the resonance position of 1440 MeV. Using HEFT, experimental scattering data is brought to the finite volume of the lattice where lattice QCD results determine the nature of the Roper resonance. Finally, these techniques are extended to the Delta-resonance spectrum providing new insight into the structure of the low-lying even-parity Delta(1600) resonance.
In Coulomb gauge QCD, there exists an instantaneous chromo-electric interaction between static quark-antiquark pairs. Studying this interaction is an effective way to probe aspects of quark confinement, as the confining behavior of this ‘Coulomb potential’ is related to the confining behavior of the Wilson potential in non-gauge fixed QCD. A clearer picture of the mechanism of confinement would then allow us to better explain aspects of the meson spectrum. We present our attempts to understand this interaction via SU(2) and SU(3) Coulomb Gauge Lattice QCD simulations on anisotropic lattices.
The hidden charm pentaquark states Pc(4312), Pc(4440), and Pc(4457) can be well assigned as \barD^(*)Sigma_c molecules, which are related by heavy quark spin symmetry. To further study the pentaquark states in the molecular picture, we have taken the heavy quark diquark symmetry to predict the Xicc Sigmac and barD T_cc molecules. Such kind of molecules belong to new molecule that are not discovered by experiment so far. If they were discovered, it will verified the molecular nature of pentaquark states. In addtion, we have predicted the hidden charm pentaquark states decaying into three-body final states in the molecular picture, which are also helpful to understand the molecular nature of pentaquark states.
We perform a unitary coupled channel study of the interaction of the $D^{*+} D^0, D^{*0} D^+$ channels and find a state barely bound, very close to isospin $I=0$. The width obtained is small, of the order of $80 \;{\rm keV}$, tied to the width of the $D^*$ states, short of the experimental one,
but which would certainly be bigger upon consideration of the experimental resolution. We perform a detailed study of the $D^0 D^0 \pi^+$ spectrum and compare with experiment, suggesting that the investigation of this state in other decay channels would bring additional new information concerning the nature of this state.
We report predictions for the suppression and elliptic flow of the Υ(1S), Υ(2S), and Υ(3S) as a function of centrality and transverse momentum in ultra-relativistic heavy-ion collisions. We obtain our predictions by numerically solving a Lindblad equation for the evolution of the heavy- quarkonium reduced density matrix derived using potential nonrelativistic QCD and the formalism of open quantum systems.
The PHENIX experiment at RHIC collected data up to 2016, primarily at CM collision energies of 200 and (for polarized pp collisions) 500 GeV/nucleon. PHENIX could measure both heavy quarkonia and open heavy flavor decays in the rapidity range -2.2 < y < + 2.2, using the muon arms and the central arm. Analysis of the very large data set collected still continues. Recently, heavy flavor results have become available from p+p, p+Au, and $^{3}$He+Au collision data collected in 2014 and 2015, as well as results from heavy ion collisions. This talk will summarize recent results on closed and open heavy flavor production from PHENIX.
Open Heavy Flavor and Quarkonia production in heavy ion collisions at RHIC and LHC.
Heavy flavored mesons produced with high pT in heavy ion collisions collisions, reveal several specific features of the production mechanism:
(i) short time of jet formation by a highly virtual heavy quark;
(ii) enhancement of the fragmentation function at large fractional momenta of the heavy meson;
(iii) extremely short time of color neutralization and formation of the heavy flavored meson wave function;
(iv) short mean free path in the medium (no color transparency);
(v) the dead-cone effect in gluon radiation, and smallness of the QCD coupling lead to a considerable reduction of the rate of broadening (transport coefficient) of heavy vs light quarks. Non-universality of q-hat is confirmed by data, which are well described.
Briefly after the Big Bang, the early universe was in a high temperature and high density environment. In order to recreate this state of matter in the laboratory, mini bangs are created by colliding heavy ions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory and subsequently at the Large Hadron Collider (LHC) at CERN. In this talk I shall be covering on the
selected results from LHC and RHIC. I shall be covering spectra and correlations (flow) and also nuclear modification factor. I shall be discussing quarkonia flow in further detail. Due to the larger mass of the bottomonium states compared to the charmonium ones,the measurement of bottomonia production in proton-nucleus collisions allows a study of CNM effects in a different kinematic
regime, therefore complementing the J/Psi studies[1]. For smaller systems like p+A and p+p we have less deeply bound bottomonia states and thus a comparatively larger chance to escape. This means that more states become measurable, which is a positive feature. On the other hand,it also means that the escape mechanism which underlies the anisotropic flow of bottomonia may become largely ineffective, in particular for the Upsilon(1S). Accordingly,the measurement of a sizable flow
for Upsilon(1S) in small systems[2] would probably hint at the importance of initial-state correlations. Our present understanding of sQGP as a very good liquid with astonishingly low viscosity will be discussed including the recent observations of QGP-like phenomena in small collision systems[3]. The understanding small systems hence becomes very important and such studies will be also stressed and presented including the opportunities which will be possible in LHC Run-3 small system data-sets.
[1] D. Das and N. Dutta, Int. J. Mod. Phys. A 33, no. 16, 1850092 (2018)
[2] D.Das , Nucl.Phys.A 1007 (2021) 122132
[3] D.Das, IJMPA Vol. 36, No. 24, 2130014 (2021)
The existence of a quasi-bound state of antikaon and nucleus, kaonic nucleus, has been discussed ever since the $\bar{K}N$ interaction in $I=0$ channel was confirmed to be strong attractive. The $\bar{K}NN$ quasi-bound state is the lightest kaonic nucleus which is considered to be $I=1/2$ and $J^\pi = 0^-$. To search for the $I_z=+1/2~\bar{K}NN$ state we conducted the J-PARC E15 experiment using in-flight $K^-$-beam at J-PARC.
Production of the $I_z=+1/2~\bar{K}NN$ state was examined by an exclusive analysis for a non-mesonic reaction, $K^-~^3{\rm He} \to \Lambda pn$, in which $\Lambda p$ pair is expected to be decay products of the $\bar{K}NN$. We observed a distinct peak in the $\Lambda p$ invariant mass spectrum at the energy region below the $\bar{K}+N+N$ mass threshold which can be naturally interpreted as a signal of $\bar{K}NN$ state.
As future prospects, there are two approaches to establish the kaonic nuclei more robustly. One is to search for heavier kaonic nuclei, and another is to study for the $\bar{K}NN$ state more precisely, especially for determination of spin and parity of the state. Thus, we have planned to perform series of experiments to study of kaonic nuclei using in-flight $K^-$ reaction at J-PARC. To perform future experiments, we will construct a new solenoid spectrometer system.
I would like to present the summary of J-PARC~E15 experiment and an overview of our future plan.
Scattering experiments involving a hyperon and a proton are the most effective methods for investigating two-body hyperon–nucleon (𝑌𝑁) interactions, as is the case in various intensive studies on 𝑝𝑝 and 𝑛𝑝 scattering, which are aimed at understanding nucleon–nucleon (𝑁𝑁) interactions. Scattering observables, such as differential cross sections and spin observables, are essential experimental inputs for constructing theoretical frameworks of 𝑌𝑁 interactions assuming a broken flavor SU(3) symmetry. However, regarding hyperon–proton scattering experiments, no experimental progress has been made from the experiments conducted throughout the 1970s in which hydrogen bubble chambers were employed. This is owing to the experimental difficulties stemming from the low intensity of the hyperon beam and its short lifetime.
A new hyperon–proton scattering experiment, dubbed J-PARC E40, was performed to measure differential cross sections of the Σ-p, Σ+p elastic scatterings and the Σ-p→Λn scattering by identifying a lot of Σ particles in the momentum region ranging from 0.4 to 0.8 GeV/𝑐 produced by 𝜋±𝑝→→𝐾+𝑋 reaction. We successfully measured the differential cross sections of these three channels with a drastically improved accuracy with a fine angular step. These new data will become important experimental constraints to improve the theories of the two-body baryon-baryon interactions.
Following this success, we proposed a new experiment to measure the differential cross sections and spin observables by using a highly polarized Λ beam for providing quantitative information on the Λ𝑁 interaction.
In this presentation, we will present the results of three Σ𝑝 channels and future prospects of the Λ𝑝 scattering experiment.
Recent and upcoming measurements using complementary observables provide an updated scenario towards the description of the low-energy $\overline{\rm{K}}$N interactions and the understanding of the nature and structure of the $\Lambda$(1405).
Among traditional approaches, the first measurement of the Kaonic Deuterium X-rays by SIDDHARTA2 will enable access to the isospin dependence of the interaction. Studies of K$^{-}$ reactions in light nuclei at DA$\Phi$NE by AMADEUS and at J-PARC by E-15 provide new measurements of cross sections and scattering amplitudes at very low momentum and the identification and characterization of the $\overline{\rm{K}}$NN state.
Two-particle correlation studies in momentum space have been recently demonstrated to be very sensitive to the effects of the final state strong interaction and are applied to K$^{-}$--p and K$^{0}$--p pairs produced in hadron-hadron collisions by the ALICE Collaboration. Such studies are now extended for the first time to Three-Body correlations.
Spectroscopy of hypernuclei with strangeness $-2$ is important to extract information on hyperon-nucleon and hyperon-hyperon interactions. In J-PARC, followed by a hybrid-emulsion experiment, a series of counter experiments with a newly constructed high-resolution spectrometer S-2S will be performed in near future. In particular, We propose an experiment (J-PARC E75 experiment) to investigate both $\Xi$ and double-$\Lambda$ hypernuclei using a $^7\mathrm{Li}$ target; in decay of $^{\,7}_{\Xi}\mathrm{H}$, which can be populated in the $^7\mathrm{Li}(K^-,K^+)$ reaction, ${}^{\ \ \ 5}_{\Lambda\Lambda}{\mathrm{H}}$ may be formed. The lightest double-$\Lambda$ hypernucleus is considered to be ${}^{\ \ \ 5}_{\Lambda\Lambda}{\mathrm{H}}$, according to many theoretical calculations, but it is yet to be discovered experimentally.
In this contribution, the overview of the $S=-2$ experiments at J-PARC is shown, with an emphasis on the E75 experiment.
The bound system of an antikaon ($\bar{K}$) and nucleons has been widely discussed based on the strong $\bar{K}N$ attraction in the isospin zero channel (I = 0). The attraction leads the much deeper binding energy of kaonic nuclei compared to that of normal nuclei. The simplest kaonic nuclei system, $\bar{K}NN$, has been one of the most expected states to be observed in the interest energy region. Recently, a few experiments (FINUDA in 2005, DISTO in 2010, J-PARC E27 in 2015 and J-PARC E15 in 2019) reported the states considered to be $\bar{K}NN$. However, the binding energies and the widths of the states were largely discrepant between the experiments. The inter-relationship between the ``$\bar{K}NN$'' has not been clearly explained experimentally nor theoretically. To improve the situation, we tried another detailed experimental approach.
Our J-PARC E31 experiment which originally aimed at $\Lambda(1405)$ spectroscopy
was also sensitive to the $\bar{K}NN$ bound states via in-flight $d(K^-, \Lambda p) \pi^-$ reaction. The reaction corresponds to the reverse reaction of J-PARC E27. In January and February 2018, we took data with approximately $3.9 \times 10^{10}$ $K^{-}$'s at 1 GeV/$c$ momentum delivered to the deuteron target. The detector system was that of J-PARC E15 so that we could apply the exclusive study same as the manner of $\Lambda p n$ in E15: detecting the $\Lambda p$ pair and identifying the rest one particle using the missing-mass method. In addition to detecting $\Lambda p$, an advantage of this reaction was the charges of all the decay particles in final states. We detected the other combinations $\Lambda \pi^-$ and $p \pi^-$ in addition to $\Lambda p$ to investigate the kinematical topologies of related processes. In a preliminary analysis, we successfully reconstructed several ten thousands of $\Lambda p \pi^-$ events in total. In this contribution, we will present the latest results of the analysis of $\Lambda p \pi^-$ final states.
Parity-violating electron scattering (PVES) is a relatively clean way to probe the weak mixing angle at intermediate energies. It also can provide information on aspects of nucleon and nuclear structure. In this talk I will review the progression in the sensitivity of PVES measurements and summarize recent results from Jefferson Lab. I will also describe the future MOLLER measurement, which will provide a measurement of the weak mixing angle that is five times more precise than the previous SLAC E158 measurement and which will serve as a sensitive probe of new physics.
Light dark matter (LDM), with masses in the MeV to GeV range, is theoretically well motivated but remarkably unexplored. The JLab Beam Dump eXperiment (BDX) is an approved proposal to collect up to 10^22 electrons-on-target (EOT) at 11 GeV during 285 days to search for LDM using a segmented CsI(Tl) scintillator detector placed downstream of the Hall A beam-dump at Jefferson Lab. This experiment will be sensitive to elastic DM-electron and to inelastic DM scattering at the level of several counts per year, probing the limit of the neutrino irreducible background. In the case of no signal, its sensitivity will allow exclusion limits to be extended by one to two orders of magnitude in the parameter space of dark-matter coupling versus mass.
In this talk, we will present the limits on LDM obtained with a pilot experiment (BDX-MINI), which accumulated 2.56 x 10^21 EOT during six months of running with the CEBAF 2.176 GeV electron beam incident on the Hall A beam dump. A blind data analysis based on a maximum-likelihood approach allowed this pilot experiment to probe the edges of existing limits on LDM, which demonstrates the discovery potential of the next generation beam dump experiment planned at intense electron beam facilities.
Belle II experiment is the perfect laboratory to search for particles that couple weakly to the Standard Model and have a characteristic decay length of a few centimetres and more. Such long lived and displaced vertex search leads to a unique signal with essentially no background. Using this methodology we show that Belle II experiment can successfully probe parameter spaces of axions, light dark gauge bosons, which are, as of now, unexplored by any other experiments.
The sensitivity of the rare decays $\eta^{(\prime)}\to\pi^{0}\gamma\gamma$ and $\eta^{\prime}\to\eta\gamma\gamma$ to signatures of a leptophobic $B$ boson in the MeV--GeV mass range is analysed in this work.
By adding an explicit $B$-boson resonance exchange, $\eta\to B\gamma\to\pi^{0}\gamma\gamma$, to the Standard Model contributions from vector meson dominance and the linear sigma model, and employing experimental data for the associated branching ratios, allows us to improve the current constraints on the $B$-boson mass $m_{B}$ and coupling to Standard Model particles $\alpha_{B}$.
From these constraints and the analysis of the available experimental $m_{\gamma\gamma}^{2}$ invariant mass distribution, we show that a $B$-boson signature in the resonant mass range $m_{\pi^{0}}\leq m_{B}\leq m_{\eta}$ is strongly suppressed and would be very difficult to experimentally identify, assuming that the $B$ boson only decays to %visible,
Standard Model particles.
In contrast, the limits outside this mass window are less stringent and the corresponding $t$- and $u$-channel signatures may still be observable in the data, as it occurs with the non-resonant, Standard Model, $\rho,\omega$ and $\phi$ meson exchanges. % contributions.
In addition, we employ experimental data from the $\eta^{\prime}\to\pi^{0}\gamma\gamma$ and $\eta^{\prime}\to\eta\gamma\gamma$ decays to explore larger $B$-boson masses.
Our results are relevant for the $B$-boson search programmes at existing and forthcoming light-meson facilities, such as KLOE(-II) and Jefferson Lab Eta Factory experiments.
The BESIII experiment has accumulated large datasets at the charmonium resonances J/ψ, ψ(3686) and ψ(3770), as well as at various other center-of-mass energies in the region between 3.8 and 4.95 GeV.
These datasets allow us to study a very huge physics program including light hadrons and their properties, charmonium spectroscopy, the production and decays of open charm mesons, and both well known and newly discovered exotic XYZ hadrons.
Recent results from BESIII as well as future perspectives will be discussed.
A class of infinite-dimensional symmetries known as asymptotic symmetries has recently been established as a universal feature of the scattering problem in generic theories of gauge and gravity. These symmetries imply an infinite number of constraints on scattering amplitudes which are equivalent to soft theorems from quantum field theory. Reciprocally, the pattern of soft radiation prescribed by the soft theorems serves as a direct signature of the underlying asymptotic symmetries. An efficient way to determine the pattern of soft radiation is through the memory effect, which detects the relative symmetry transformations induced by soft radiation on pairs of test charges. In short, configurations of soft radiation can be reconstructed from their distinct imprints on an array of test charges. I will present a set of asymptotic symmetries that arise in classical non-Abelian gauge theory and their associated "color memory" effects. Then, I will discuss how these classical color memory effects are ubiquitous in high-energy processes occurring at particle colliders.
Electromagnetic Form factors give information on internal dynamics of hadrons. They are
theoretical input to the hadron electromagnetic current in calculation of the structure of
hadrons. Their direct measurement in the spacelike and timelike kinematic regime,
respectively, is made through differential cross sections and polarization observables of
electron scattering and electron-positron annihilation reactions. In this talk I review on how
a variety of recent experimental data on low-lying nucleon resonance electromagnetic
excitations can tell us about the evolution of the relevant degrees of freedom and the
photon-baryon couplings. The importance of multiquark meson-baryon decay channels and
meson-cloud configurations is addressed within a relativistic quark model calculation.
Spin is a unique probe to unravel the internal structure and QCD dynamics of nucleons. Exploration of the 3D spin structure of the nucleons is based on the complementarity of lepton scattering processes and purely hadronic probes. Some of the main questions that physicists have been trying to address in spin experiments involving different interactions and probes are: How does the spin of the nucleon originate from its quark, anti-quark, and gluon constituents and their dynamics? What can transverse-spin phenomena teach us about the structure of the nucleon and properties of QCD? In my talk, I will give an overview of selected recent results and future opportunities from the experimental campaigns probing the spin structure of nucleons utilizing both lepton scattering processes and hadron-hadron interactions, like Jefferson Lab experiments with electron beam, COMPASS muon-beam and Drell-Yann program, as well as the RHIC-Spin program with pp collisions.