Ignore any e-mails not coming from the organizers or indico related to this meeting! They are phishing attempts with promises of booked hotels etc.
POETIC XI, the eleventh international conference on the ‘Physics Opportunities at an Electron-Ion Collider’, follows POETIC X which took place at the iICTP-SAIFR, São Paulo, Brazil in May 2023.
The primary goal of the conference is to continue the advancement of the field of the future Electron-Ion Collider (EIC) physics which was granted Critical Decision 3A (CD-3A) by the U.S. Department of Energy (DOE) and will be built at Brookhaven National Lab in New York in partnership with the Jefferson Lab (JLab). This collider will be a first-of-its-kind research machine and will push the limits of our knowledge of quantum chromo dynamics, accelerator science, particle detector design, high-performance computing and more.
An important tool in studying the sub-femtoscale spacetime structure of matter in ultrarelativistic heavy-ion collisions is Hanbury-Brown-Twiss (HBT) intensity interferometry of identical particles in the final state of such collisions. We propose that a variant of the entanglement enabled intensity interferometry (E2I2) framework introduced by Cotler and Wilczek can provide a powerful alter- native to HBT interferometry in extracting fundamental nonperturbative features of QCD at high energies. We apply this framework to demonstrate that the spatial distributions of color singlet (pomeron) configurations in nuclei are sensitive to measurements of exclusive resonant decays of ρ-mesons into π±-pairs in ultrarelativistic ultraperipheral nuclear collisions (UPCs) at RHIC and the LHC. A preliminary analysis suggests that model-independent extract of pomeron distributions will require careful treatment of the interplay of E2I2 in the vector meson exclusive decay with the incoherent cross-section for exclusive vector meson production. The E2I2 framework developed here is quite general. It can also be employed as a tool to extract information on the spin structure of pomeron couplings as well as enhance the discovery potential for rare odderon configurations from exclusive vector meson decays into few-particle final states both in UPCs and at the Electron-Ion Collider.
In recent years, Low’s soft theorem up to sub-leading order has garnered renewed interest due to its deep connection with asymptotic symmetries. In this talk, I will demonstrate that, in the small x limit, Low’s soft theorem can be derived from a quasi-classical field approach by solving classical Yang-Mills equations up to sub-eikonal order. Furthermore, I will discuss how gluon saturation can be incorporated into Low's soft theorem and explore the potential for studying gluon saturation through the lens of asymptotic symmetries.
Since baryon is a composite particle, one may wonder which degrees of freedom are carrying the conserved charges, including the baryon number. A baryon junction, that arises naturally in a gauge-invariant description of the baryon wavefunction, is a perfect candidate to associate the baryon number with. In this talk I will discuss various possibilities to test the flow of baryon number experimentally, including the recent proposal of studying semi-inclusive deep inelastic scattering. The rapidity distribution of baryons produced in high-energy processes depends crucially on the Regge intercepts of exotic states with hidden baryon number. I will go over recent developments in the Feynman-Wilson analog gas model that can be used to estimate such intercepts. Finally, I will explore the possibility of identifying such exotic states as glueballs with lattice QCD.
We analyze the thermalization of jets in QED2 in detail. In particular, we identify the emergence of an effective temperature. Moreover, we compute the quasiparton distributions of the lightest meson in massive QED2. For increasing rapidity, we compute the spatial quasiparton distribution functions and amplitude for the lowest excited state numerically both at strong and weak coupling and compare them to light front results in the lowest Fock space approximation. Moreover, we introduce the concept of the quark quasifragmentation function (qFF) using an equal-time and spatially boosted form of the Collins-Soper fragmentation function where the out-meson fragment is replaced by the current asymptotic condition. In the massive Schwinger model, we compute the qFF by exact diagonalization of the spin Hamiltonian. Finally, we compare the results to the qFF following from the Drell-Levy-Yan result for QED2 and to QCD2 in the lowest Fock approximation.
Starting from the Weinberg formalism for fields of arbitrary spin, we discuss a method for the decomposition of matrix elements of QCD operators (local currents, quark/gluon bilinears) for targets with arbitrary spin. This procedure is advantageous for the systematic study of the structure of hadrons and nuclei, particularly in the case of spin-dependent observables. As higher spin targets exhibit new features in their hadronic structure, the investigation of these properties can enhance our understanding of the strong force.
The construction allows for a unified framework to discuss spin > 1/2 very similar to the spin 1/2 case, without subsidiary conditions for the wave functions. Different types of spinors (canonical, helicity, light-front helicity) can be easily accommodated. Its numerical implementation is simple and can be entirely reduced to objects familiar from the rotation group. The study of spinor bilinears basis reveals a natural sl(2,C) multipole decomposition. This enables the physical interpretation of non-perturbative objects that multiply the bilinears as Generalized Form Factors.
To demonstrate the efficacy of this method, we apply it to the description of a spin 1 target, such as the deuteron. We discuss extensions of the formalism to hard exclusive processes on the deuteron and beyond.
*This work is supported by NSF awards 2111442, 2239274, and 2316701.
A new global QCD analysis by the JAM collaboration performs the first extraction of transversity PDFs and tensor charges using both the Transverse Momentum Distribution (TMD) and Dihadron Fragmentation Function (DiFF) channels simultaneously, including all currently available experimental data. Known theoretical constraints on transversity, namely, its small-$x$ asymptotic behavior and the Soffer bound, are incorporated in the fit. We test compatibility with lattice-QCD calculations for the tensor charges by including them in the fit, in order to further examine whether there is a universal nature to all of the available information on transversity distributions and tensor charges of the nucleon
We investigate the quark transversity parton distribution functions (PDFs) in the nucleon within the framework of a covariant and confining Nambu-Jona-Lasinio (NJL) model. The nucleon bound state is obtained by solving the Faddeev equation in the quark–diquark approximation. The parameters of the model are fitted to the well-known experimentally measurable quantities such as the proton mass, pion mass, and pion decay constant. After that, the PDFs can be obtained by straightforwardly evaluating Feynman diagrams. In contrast to the earlier work, we include not only the scalar and axial vector diquark channels but now also the pseudoscalar and vector diquarks. The inclusion of these new diquark channels is crucial in maintaining chiral symmetry. We present the transversity quark PDFs in our new model and compare them to the available empirical fits. In our new model, we treat the Dirac matrix $\gamma_5$ with extreme caution due to the well-known issue of $\gamma_5$ once a regularization scheme is applied. Our model, along with the application of our self-consistent regularization prescription (SCRP) and the treatment of $\gamma_5$ in the Larin scheme, preserves the Ward identity, satisfies the axial anomaly, and gives consistent result for the two formally equivalent transversity operators.
We report a lattice QCD study of iso-vector helicity transverse momentum-dependent distributions (TMDs) and flavor-dependent unpolarized TMDs of $u$- and $d$-quarks. Utilizing domain-wall fermion discretization with physical quark masses and a fine lattice spacing of $a$ = 0.0836 fm, we compute both conventional gauge-invariant (GI) quasi-TMDs and the novel Coulomb-gauge-fixed quasi-TMDs. Based on the factorization to the light-cone TMDs under the framework of large momentum effective theory (LaMET), we extract the renormalization-group-invariant (RGI) ratios between these three TMDs as functions of longitudinal momentum fraction $x$ and transverse separation $b_T$. Our results are compared with recent global analyses of helicity and unpolarized TMDs. Additionally, we discuss the connection between the three-dimensional TMDs and the one-dimensional parton distribution functions.
Hadronization processes, how particular hadrons are formed from scattered quarks and gluons (partons), is a key area of study in high- energy physics. The Belle II experiment at the asymmetric e+e- collider SuperKEKB offers a high-statistics, clean initial state to extract and refine our understanding of hadronization, including Fragmentation Functions (FFs), which describe the probability distribution of a parton fragmenting into a specific hadron. Ongoing and prospective measurements at Belle II related to di-hadron FF (DiFF), Transverse Momentum Dependent (TMD) jet function, polarizing FF, as well as probing $\Lambda$ spin correlation, will be discussed. This talk will highlight the importance of Belle II data in understanding FFs and their implications for future Electron-Ion Collider (EIC) measurements.
We discuss exclusive $\phi$-meson electroproduction off the proton near threshold within the GPD factorization framework.
We propose the "threshold approximation" in which only the leading term of the
conformal partial wave expansion of the process amplitudes
is kept in both the quark and gluon exchange channels.
We test the validity of this approximation to next-to-leading order in QCD
and demonstrate the strong sensitivity of the cross section to the gluon
and strangeness gravitational form factors.
We also perform realistic event generator simulations both for Jefferson Lab
and EIC kinematics and demonstrate the capabilities of future facilities
for measuring near-threshold $\phi$ production.
Azimuthal modulations are crucial in the phenomenological extraction and separation of various generalized parton distributions (GPDs). Traditionally, GPDs could be extracted from angular modulations of the deeply virtual Compton scattering (DVCS) in the Breit frame. However, the Bethe-Heitler subprocess (BH) interferes with the DVCS and contaminates the azimuthal modulations from DVCS, making it challenging to extract GPDs cleanly. We provide a new formalism and choice of frame to describe the azimuthal distributions, and demonstrate that they are more suitable for experimental analysis to separate contributions to a physical cross section from GPD sensitive (such as DVCS) and insensitive (e.g., BH) subprocesses in a consistent and uniform way.
Hadron matrix elements of the QCD energy-momentum tensor are expressed by the gravitational form factors. The gravitational form factors are related to a particular moment of the GPDs, and are relevant to EIC physics. The forward (zero momentum transfer) values of the gravitational form factors allow for a decomposition of the hadron mass into the contributions from quarks and gluons, and the further subdivisions into the contributions from quark masses and from the QCD trace anomaly may be considered. This talk presents the most recent evaluations of these mass decompositions for the nucleon, using a quantitative evaluation of the forward values of relevant gravitational form factors at next-to-next-to-leading order (three-loop) QCD. We discuss the renormalization scale dependence of each component within these decompositions. We also present the results for the pion, which exhibit distinctly different behaviors from the nucleon. This talk is based on my papers, JHEP 01 (2019) 120, JHEP 03 (2023) 013, and on a new paper in preparation.
The gluon density inside nucleons has been observed to increase rapidly with energy, which would eventually violate unitarity. At high energies, however, nonlinear effects start to become important, slowing down the evolution of the gluon density and giving rise to gluon saturation. While there have already been strong hints of saturation effects in the currently available data, definite evidence of saturation is still lacking. As exclusive vector meson production is a process that is very sensitive to the gluon density, it offers one possible channel for measuring gluon saturation.
The purpose of this talk is to study the magnitude of saturation effects in exclusive heavy vector meson production [1]. This is done by comparing predictions from linear and nonlinear models for the evolution of the gluon density, described using the color-glass condensate effective field theory. The difference in these models is the high-energy evolution of the dipole amplitude which is done according to the BFKL and BK equations. We find that saturation effects are negligible for proton targets, but heavy nuclear targets show a strong indication for gluon saturation already in the currently available data.
[1] J. Penttala, C. Royon, arXiv:2411.14815 [hep-ph]
Unveiling chiral-odd dimeson generalized distribution amplitudes
S. Bhattacharya, R. Boussarie, B. Pire, L. Szymanowski
Chiral-odd generalized distribution amplitudes which are the crossed matrix elements from chiral-odd quark GPDs in a meson contain valuable information on the transversity (or tensor) structure of mesons.
They are up to now inaccessible to experimental investigation. We study a new reaction which allows to separate them from known quantities: exclusive electron positron annihilation into two back to back pion pairs of moderate invariant mass, through two photon exchange : $e^- e^+ \to \gamma^* \gamma^* \to (\pi \pi)_1 (\pi \pi)_2$. In the case of the production of two charged dimeson ($\pi^+\pi^0$) and ($\pi^-\pi^0$), this process interferes with a process with a single photon $e^- e^+ \to \gamma^* \to (\pi^+\pi^0) (\pi^-\pi^0)$. A direct measure of this interference is possible through the study of charge-conjugation odd observables such as the forward - backward asymmetry of the $\pi^+\pi^0$ cross section. Such studies may be performed at BES III or BELLE 2 facilities.
We use the GUMP (Generalized Parton Distributions (GPDs) through Universal Moment Parametrization) framework, based on the conformal moments of GPDs, to perform a unified global analysis incorporating Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) data. By performing simultaneous fits across these processes and incorporating Next-to-Leading Order (NLO) corrections, we are able to constrain the valence quark, sea quark and gluon GPDs.
We investigate the off-shell pion electromagnetic
form factors using phenomenological relativistic
constituent quark models. These models, which treat the
pion as a composite of massive, structureless quarks,
employ the Mandelstam approach to calculate the
microscopic form factors. Each model is parameterized by
two scale parameters fitted to the pion decay constant and charge radius.
Experimental data from the exclusive Sullivan process,
$^1$H$(e,e',\pi^+)n$, analyzed within the framework of pion pole dominance and under the condition of low off-shell virtuality, enabled the comparison between our previous model predictions and the extracted off-shell pion form factors. One of the two off-shell form factors, inaccessible through conventional elastic electron scattering experiments, is obtained from the
exclusive Sullivan process cross-section data
via a relation derived from the Ward-Takahashi identity
for the pion electromagnetic current.
References
Off-shell pion properties: Electromagnetic form factors and light-front wave functions.
Jurandi Leão,J. P. B. C. de Melo,T. Frederico, Ho-Meoyng Choi and and Chueng-Ryong Ji.
Phys. Rev. D110, 074035 (2024).
Pion off-shell electromagnetic form factors:
Data extraction and model analysis.
Ho-Meoyng Choi,T. Frederico, Chueng-Ryong Ji, J. P. B. C. de Melo.
Phys. Rev. D100, 116020 (2019).
The light-front wave functions (LFWF) of hadrons can be obtained by projecting their Bethe-Salpeter wave functions on the light front. The latter is obtained within a functional approach to QCD, solving first the quark gap equation within a chiral-symmetry preserving truncation scheme and then the Bethe-Salpeter equation for pseudoscalar and vector mesons. With the LFWF we derive the meson’s parton distribution function (PDF), transverse momentum distribution (TMD) and generalized parton distributions (GPD) of light and heavy mesons as well as quarkonia. Quark-fragmentation functions and their generalization to jet functions are obtained within the same framework. The insights of these studies serve to prepare the field for nucleons, which are the real object of interest at the EIC.
In this talk, we will discuss the synergies between the physics results and prospects of ultra-peripheral heavy-ion collisions (UPC) at the LHC and those at the Electron Ion Collider (EIC). We will emphasize studies of gluon saturation and low-x physics, highlighting the connections and complementarities enabled by future LHC detector upgrades. Finally, we will discuss some of the experimental and theoretical challenges, and describe how UPC results and detector projects will foster new experimental and theoretical efforts for the electron-proton and nucleus program at the EIC.
We introduce the ``target jet" in the forward region of the ion in deep inelastic scattering (DIS) events with a jet radius which depends on the DIS kinematics in order to separate the current and target regions in the laboratory frame. We show that target jet substructure and its correlation with the substructure of the leading jet is sensitive to the internal structure of nucleon and ion, thereby motivating the design of forward detectors to fulfill target jet substructure phenomenology at the future Electron Ion Collider. Combining target jet charge and leading jet charge significantly improves the identification of the hard scattering flavor structure in electron-proton collisions. Furthermore, forward neutron tagging allows an isolation of an almost pure up-quark jet sample, which could be used to enhance sensitivities to flavor-dependent effects such as Sivers asymmetry. We demonstrate the connections between target jet energy flow observables and parton distributions, as well as the mapping between forward nuclei tagging and details of nuclear breakup process such as the location of the DIS nucleon.
I will discuss low-energy nuclear physics at the future Electron-Ion Collider (EIC) at Brookhaven. By comparing the standard theory of electron-nucleus scattering with the equivalent photon method applied to Ultraperipheral Collisions (UPC) at the Large Hadron Collider (LHC) at CERN. In the limit of extremely high beam energies and small energy transfers, very transparent equations emerge. We apply these equations to analyze nuclear fragmentation in UPCs at the LHC and $eA$ scattering at the EIC, demonstrating that the EIC could facilitate unique photonuclear physics studies. However, we have also shown that the fragmentation cross-sections at the EIC are about 1,000 times smaller than those at the LHC. At the LHC, the fragmentation of uranium nuclei displays characteristic double-hump mass distributions from fission events, while at the EIC, fragmentation is dominated by neutron emission and fewer few fission products, about 10,000 smaller number of events.
In this talk I will review the lattice QCD calculation of TMD physics and its impact on the experiments at the future Electron-Ion Collider. I will discuss the theory development centering around the large-momentum effective theory (LaMET) and the newly proposed Coulomb-gauge correlation functions within this framework. Besides, I will review the systematic lattice calculation of the Collins-Soper evolution kernel, and the spin-dependent TMD parton distribution functions, which have undergone significant improvement in the past few years.
The study of the nucleon's 3-D momentum and spin structure emerged from studies of both leading power (LP) and next-to-leading power (NLP) contributions to SIDIS observables. Although typically suppressed by $\Lambda_{\tiny QCD}/Q$, an understanding of the NLP TMD observables is essential for accurately describing SIDIS, and for properly extracting LP effects from SIDIS data. A key NLP observable, the $\cos\phi$ azimuthal modulation (Cahn effect), has been crucial in the development of the TMD field. Recent COMPASS measurements of the Cahn-effect have reaffirmed its importance in probing the nucleon’s 3-D structure. Additionally, the HERMES collaboration's observation of the Sivers effect via a power-suppressed target single-spin-asymmetries (SSA) for pion production underscored the importance of NLP contributions.
In this talk, I will review the phenomenology and theory of leading and next to leading power TMD observables in semi-inclusive scattering processes. I present our latest work on establishing TMD factorization at NLP, emphasizing the role of renormalization group consistency and the criteria for matching large and small transverse momenta in the cross section. Establishing TMD factorization at NLP is essential for 3-D imaging of hadrons in current and future DIS experiments, as well as for advancing global analyses of transverse SSA studies in the EIC era.
Semi-Inclusive Deep Inelastic Scattering (SIDIS) is a core physics program at the future Electron-Ion Collider. Precision measurements with the ePIC detector at the EIC will elucidate the polarized and unpolarized quark-gluon structure of the nucleons and nuclei with an unparalleled combination of kinematic reach, phase space, and precision. The ability of the EIC to accelerate a wide range of nuclei in addition to protons will also have a profound impact on our understanding of hadronization.
This talk will give an update on the respective SIDIS studies at ePIC and how the SIDIS program will fit in with the planned early physics program.
Incoherent DVCS on a Deuteron target provide a way to extract Compton form factors of the neutron. Compton form factors are a convolution of a hard kernel with GPDs. The neutron GPDs provide quark flavor separation in GPDs. In modeling unpolarized incoherent DVCS on Deuteron we use a lightfront wavefunction to factorize nuclear and nucleonic structure in DVCS. In addition to DVCS amplitude, Bethe-Heitler must be taken into account in cross section.
Proton anti-proton production has been used to search for possible intermediate systems in various experiments.
Evidence for a potential narrow resonance in the $p\bar{p}$ system is scarce, while there is no evidence for
a wide resonance in the $p\bar{p}$ system in either photoproduction or electroproduction. Previous high statistic
photoproduction analyses have focused on the extraction of cross-sections and have found no evidence of a potential
narrow resonance; the production mechanism of the $p\bar{p}$ still remains unclear. In this work, we use Run Group
A data from the CLAS12 collaboration at beam energies of $10.2GeV$ and $10.6GeV$ to perform the first high statistic
electroproduction analysis of $p\bar{p}$. Basic data features and preliminary analysis results will be presented.
In this talk, I will present two approaches for extracting the total gluon helicity contribution to proton spin from lattice QCD, one from local operator matrix elements in a fixed gauge accessible on lattice with feasible renormalization, and the other from gauge-invariant nonlocal gluon correlators. Neither of these approaches requires a matching procedure when converted to the MS scheme. Our proposal resolves a long-standing inconsistency in the literature regarding lattice calculations of the total gluon helicity and has the potential to greatly facilitate these calculations.
We propose a novel method to probe light-quark dipole moments by examining the azimuthal asymmetries between a collinear pair of hadrons in semi-inclusive deep inelastic lepton scattering off an unpolarized proton target at the Electron-Ion Collider. These asymmetries provide a means to observe transversely polarized quarks, which arise exclusively from the interference between the dipole and the Standard Model interactions, thereby depending linearly on the dipole couplings. We demonstrate that this novel approach can enhance current constraints on light-quark dipole operators by an order of magnitude, free from contamination of other new physics effects. Furthermore, it allows for a simultaneous determination of both the real and imaginary parts of the dipole couplings, offering a new avenue for investigating potential $CP$-violating effects at high energies.
The deuteron electro-disintegration $D(e,e'p)n$ experiment aims to measure D(e,e'p)n cross sections at high $Q^2$, $x_{Bj} > 1$, and missing momenta $p_m>600$ MeV/c with great statistical precision. To obtain a greater understanding of the strong nuclear force, we must probe the nucleus at sub-fermi distances where the nucleons overlap. In this region, the nucleon-nucleon (NN) potential is not well understood as there is a lack of experimental data for missing momenta beyond $500$ Mev/c 1. The deuteron is the simplest bound NN system, which makes it the perfect starting point for understanding the strong nuclear force, especially at extremely short distances. This experiment was conducted in Experimental Hall C of Jefferson Lab (JLab). JLab houses the Continuous Electron Beam Accelerator Facility (CEBAF). In this experiment, CEBAF's 11 GeV electron beam is incident on a liquid deuterium target, and the recoil proton and electron are detected by Hall C's High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS), respectively. The recoil neutron momentum, i.e., the missing momentum, is then reconstructed from the reaction's kinematics. This ideal reaction, in which the momentum of the nucleons can be directly correlated, is described by the plane wave impulse approximation (PWIA). Other short-range correlation processes (final state interactions (FSI), meson exchange currents (MEC), and isobar configurations (IC)) can be suppressed under carefully selected kinematics 1. Previous results published by C.Yero et. al. 2 showed a discrepancy between the data and the non-relativistic theoretical models in the large missing momentum regime. In the spring of 2023, we took data up to even higher missing momenta, which will allow us to extend the cross-section domain beyond 1.0 GeV with great statistics. The data is currently being analyzed and should be ideal for testing fully relativistic deuteron wave function models. In this poster, I present an overview of the experiment as well as an update on the current analysis.
I would like to thank my professors Werner Boeglin and Misak Sargsian. This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under the contract DE-SC0013620.
We calculate the elastic production of dijets from electron collisions with a longitudinally polarized proton target at small values of the Bjorken $x$ variable. Building on the pioneering proposals of [1-3] for measuring the quark and gluon orbital angular momentum (OAM) distributions, our focus is on both the longitudinal double spin asymmetry (DSA) and longitudinal single spin asymmetry (SSA). We compute the numerators of these asymmetries in the small-$x$ formalism of the light-cone operator treatment (LCOT). Utilizing the small-$x$ expressions for the OAM distributions derived earlier in [4], we demonstrate that the DSA provides a robust probe for both the quark and gluon OAM distributions within the proton. In contrast, we find that while the SSA is also sensitive to the OAM distributions, extraction of the latter from the SSA would require new developments in small-$x$ theory and phenomenology, and is probably not feasible at this point in time. These findings highlight the potential of DSA measurements in elastic dijet production at the future Electron-Ion Collider (EIC) to provide the first-ever direct access to the quark and gluon OAM distributions at small $x$, paving the way for new insights into the proton spin puzzle.
[1] Y. Hatta, Y. Nakagawa, F. Yuan, Y. Zhao and B. Xiao, Gluon orbital angular momentum at small-$x$, Phys. Rev. D95 (2017) 114032 [1612.02445].
[2] S. Bhattacharya, R. Boussarie and Y. Hatta, Signature of the Gluon Orbital Angular Momentum, Phys. Rev. Lett. 128 (2022) 182002 [2201.08709].
[3] S. Bhattacharya, D. Zheng and J. Zhou, Probing the Quark Orbital Angular Momentum at Electron-Ion Colliders Using Exclusive $\pi_0$ Production, Phys. Rev. Lett. 133 (2024) 051901 [2312.01309].
[4] Y.V. Kovchegov and B. Manley, Orbital angular momentum at small $x$ revisited, JHEP 02 (2024) 060 [2310.18404].
Particle collider experiments are generally driven by the attempt to discover new particles and perform exact measurements of physical phenomena. The main purpose of those experiments is to find out the discrepancies from the current theoretical measurable properties of matters. Traditionally, photomultiplier tubes (PMTs) have been extensively used to detect scintillation light in particle collider experiments. In recent years, silicon detectors have gained interest as radiation detectors in particle, nuclear, and atomic physics. One of the important applications is in particle collider experiments for their high-energy resolution and excellent signal-to-noise ratio, even with thin designs and precise particle tracking enabled by micro-patterning for unmatched spatial resolution. silicon photomultipliers, an array of single photon avalanche diodes (SPADs) based silicon detectors have become preferable as a solid-state alternative to PMTs due to their invulnerability to magnetic fields, compactness, low operating voltage, robustness, and lower cost. Furthermore, SPADs implemented in a standard CMOS process, as opposed to a dedicated optical process, allow the optical sensor to be coupled on the same chip with the readout electronics. This results in a compact, low-cost, and low-bias voltage SiPM detector. However, SiPMs tend to rapidly degrade in high irradiation environments, making them unsuitable for some collider experiments, particularly given the trend towards higher luminosities and therefore higher irradiation levels. One of the major challenges of SiPM in such high-radiation environments is their noise performance. This idea involves integrating innovative perimeter field gates into SPADs within commercial CMOS processes to create perimeter-gated SPADs. Preliminary work has shown that the field modulating gate reduces the noise (dark count) of regular SPADs and SPAD-based SiPM detectors. The proposed high-performance SPADs show great potential for future particle collision experiments.
We investigate the impact of future measurements at the electron-ion collider (EIC) and Jefferson Lab (JLab) on the nucleon's transversity distributions and tensor charges, focusing on dihadron production in semi-inclusive deep inelastic scattering.
For this study, we use EIC pseudo-data for a proton target, as well as JLab (CLAS and SoLID) pseudo-data for proton, deuteron, and $^3$He targets.
We find that future EIC data can considerably constrain the nucleon transversities, especially at low $x$.
Future JLab data can lead to significant constraints in the large-$x$ region and provide new information on whether there is tension between the tensor charges extracted from experimental data and those obtained in lattice QCD.
One of the major goals of the Electron-Ion Collider (EIC) is to better understand nuclear structure at high energy. A principal measurement is coherent exclusive vector meson (VM) production in diffractive e + A collisions. The gluon spatial distribution inside the nucleus can be obtained through a Fourier transform of the nuclear momentum transfer (|t|) distribution for these vector mesons. However, the |t| distribution is one of the most challenging measurements at the EIC. There are two main obstacles in this measurement that this research aims to overcome: limited precision in measuring |t| and large background from incoherent events that govern most of the |t| regime, making it difficult to resolve the diffractive pattern from coherent events. We employ a method for reconstructing |t| by utilizing the electron beam polarization in e + A collisions and measuring the projected |t| distribution to overcome those complications. This technique will allow us to statistically separate incoherent and coherent events and precisely measure the diffractive pattern, providing a potential solution for a critical measurement that is difficult for the EIC baseline detector. Through the study of diffractive vector meson production, we carry out an experimental simulation of how the detector effect would change the extracted nuclear geometry and how to use projective techniques to avoid defects. Previous methods for studying heavy-ion collisions can be applied to investigate exclusive VM production in this research. This would be informative for EIC experimental measurements in the future.
Recently, a novel approach has been suggested to compute parton distributions through the use of boosted correlators fixed in the Coulomb gauge from lattice QCD, within the framework of Large-Momentum Effective Theory (LaMET). This approach circumvents the need for Wilson lines, potentially enhancing the efficiency and accuracy of lattice QCD calculations significantly. In this study, we implement the Coulomb gauge method to calculate the unpolarized and helicity parton distribution functions (PDFs) of nucleons. Following a careful investigation of the excited state contamination and various systematic uncertainties, we provide final results of the nucleon PDFs obtained from lattice calculations, which show compatibility with global fits. This research also serves as a benchmark for future broader applications of the Coulomb gauge method, particularly in the computation of transverse-momentum-dependent distributions.
The PrimEx-eta experiment conducted in Hall D at Jefferson Lab, aims
to extract the radiative decay width of the η meson. This experiment serves
as a probe to test fundamental symmetries in low energy QCD by exploiting
the Primakoff effect, specifically by measuring the η meson photoproduction
cross section on a Helium-4 target. Additionally, it will provide valuable in-
put to determine the light quark mass ratio and the mixing angle between η
and η′ mesons. Furthermore, it will contribute by providing an additional data
point to complement previous results for the η radiative decay width obtained
through leptons colliders and a single Primakoff measurement which unfortu-
nately yielded a significantly lower value compared to the collider result. The
GlueX collaboration concluded taking data on 2022 using the GlueX detector.
Preliminary results will be presented for the charged decay channel for the 2022
data.
Understanding the transverse momentum-dependent distributions (TMDs) in semi-inclusive deep inelastic scattering (SIDIS) is essential to explore the three-dimensional nucleon structure.
In this presentation, we discuss extending this framework into the nuclear domain, where TMDs enable investigating of nuclear effects.
This study explores the modifications induced by nuclear medium on SIDIS observables, specifically on their transverse momentum (${p_{t}}$) and momentum-fraction ($z$) dependencies.
For this analysis, we use the data collected in the Fall of 2023 by the CLAS Collaboration at Jefferson Lab. The experiment used a 10.5 GeV polarized electron beam impinging on various nuclear targets:
such as liquid deuterium and a set of solid foils (C, Cu and Sn).
We will present our first preliminary results of the $\pi^{+}$ electroproduction in the SIDIS regime and compare these results with an existing Monte Carlo simulation.
Then, we will show the necessary corrections still to be applied to the data and the limitations of the ongoing analysis.
Finally, we will discuss how the present data can offer an insight into the transverse momentum structure of partons in nuclei regarding the current status of nuclear TMDs phenomenology.
Two key objectives of the future Electron-Ion Collider (EIC) are to explore the 3D structure of hadrons—via Transverse Momentum Dependent distributions (TMDs) and Generalized Parton Distributions (GPDs)—and to understand gluon saturation at small-x, as described by the Color Glass Condensate (CGC) effective field theory. This talk focuses on observables that bridge these complementary goals of the EIC. Specifically, I will present a study of transverse energy-energy correlators in back-to-back electron-hadron production during electron-proton collisions in the small-x regime. I will demonstrate how polarization effects can be probed by connecting the quark Sivers function at small-x to the Odderon dipole amplitude within the CGC framework. This approach enables the computation of Sivers asymmetries and polarized transverse energy-energy correlators in collisions of unpolarized electrons with transversely polarized protons, providing novel insights into transverse dynamics, polarization effects, and gluon saturation phenomena.
The chiral anomaly in polarized deeply inelastic scattering manifests itself as an infrared pole of the box diagram in exact off-forward kinematics. The mechanism of the pole regularization is extremely subtle. I will show that such mechanism in QCD is fundamentally different from QED where the anomaly pole vanishes for finite lepton mass. Instead in QCD the mechanism has to do with the physics of the chiral anomaly and the topology of the QCD vacuum, which allows to relate the net quark helicity to the slope of the topological susceptibility of the QCD vacuum.
There have been rapid developments in the direct calculation in lattice QCD (LQCD) of the Bjorken-x dependence of hadron structure through large-momentum effective theory (LaMET) and other similar effective approaches. These methods overcome the previous limitation of LQCD to moments (that is, integrals over Bjorken-x) of hadron structure, allowing LQCD to directly provide the kinematic Bjorken-x regions where the experimental values are least known. In this talk, I will show some selected recent progress along these directions and examples of how including lattice-QCD calculations in the global QCD analysis can play a significant role in improving our understanding of parton distributions in the future.
Generalized parton distributions (GPDs) are functions of four variables, one of which is a renormalization scale. The functional dependence on this renormalization scale is fully determined by a renormalization group equation---or "evolution equation"---that can be derived from perturbative QCD. A fast numerical implementation of the scale evolution is vital to any global phenomenology effort. Moreover, for a framework leveraging neural networks, differentiability is also necessary. In this talk, I will discuss an ultra-fast, differentiable implementation of GPD evolution in momentum fraction space, in which the evolution equation itself is (approximately) rendered as a differential matrix equation.
In the first part of this talk, I will introduce the EpIC Monte Carlo event generator for exclusive processes. Built on the PARTONS framework, EpIC offers a variety of model options and a flexible structure for DVCS, TCS, DDVCS and several DVMP processes. A key feature of EpIC is the integration of second-order radiative corrections, enhancing its precision for theoretical studies. As a result, EpIC provides a comprehensive toolset for probing nucleon structure through impact studies at future electron-ion colliders.
In the second part of the talk, I will discuss the impact of EIC pseudo-data on nucleon tomography and Compton form factors, as obtained from detector simulations using the EICROOT package containing the full far-forward detector region needed for tagging and reconstructing the scattered proton. In order to reconstruct the scattered electrons and DVCS photons a parametrized central detector region was used. These two components combined mimic the full capabilities of the first EIC detector, known as ePIC.
I will present recent updates from the CTEQ-JLab (CJ) global PDF analysis. These include the effort to put together a world DIS database, the extraction of PDFs and neutron structure function F2 at large x, and the analysis of the systematic uncertainty due the interplay of higher-twist and off-shell nucleon modification in deuteron targets. I will then discuss how future experiments and facilities, especially the EIC, will improve our understanding of PDFs and nuclear effects.
We discuss the current status of the extraction of nuclear Parton Distribution Functions (nPDFs) and highlight the opportunities that experimental measurements at the EIC can provide. Specifically, we focus on recent improvements and challenges on the determination of the nuclear Strange and Gluon distributions, the flavor separation and the dependence on the nuclear mass number $A$. Each of these challenges can be approached via the precision measurements the EIC is designed for.
Further, we discuss a newly developed phenomenological approach to the determination of nPDFs that is inspired by short ranged correlated (SRC) nucleon pairs. Early studies indicate, that a connection between high-energy phenomenology and nuclear modeling can be established. The measurements at the EIC will help unravel this mystery and ultimately provide a better understanding of the nuclear structure.
The study of nuclei through the lens of quark and gluon degrees of freedom remains a rich frontier in nuclear physics. The EIC presents a unique opportunity for important discoveries that could help unravel longstanding mysteries around how quark-gluon dynamics differs between proton and nuclear systems. This presentation will explore these opportunities and showcase some new results.
Central goals of nuclear physics are to understand the spatial structure of the proton, as well as the mechanisms that generate its mass and spin distributions, emerging from quark and gluon interactions via the strong force in QCD. Vast resources have been committed to experimental facilities - foremost the upgraded 12 GeV Jefferson Lab accelerator and the planned Electron-Ion Collider (EIC) that have been paralleled, more recently, by a remarkable shift in federal science and technology investments in AI. I will discuss how AI-based approaches allow us to solve the complex problem of determining spatial structure at the femtoscale, illustrating, with a practical application to deeply virtual exclusive scattering, how this can bring about breakthroughs that were once thought impossible. Explainable AI approaches are producing new avenues in theoretical physics while generating innovative ideas across fields.
Having more than one detector is essential for independent cross checks of results and confirmation of discoveries. This was recognized as a guiding principle in the past, and will be of particular importance for the EIC, which will be a unique facility worldwide. Experience from HERA also shows that if the two detectors are not too different, data can be combined, reducing the overall systematic uncertainties. This would be even more important at the EIC, as its much higher luminosity means that more measurements will be limited by systematics. A 2nd detector can also expand the science program of the EIC. An interaction region incorporating a second focus could, for instance, greatly improve the acceptance for recoiling light ions and low-x / low-t protons from exclusive reactions and enable detection of the complete nuclear final state in reactions where the nucleus breaks up. Application of the latter could include efficient vetoing of breakup and studies of exotic fragments such as hypernuclei and rare isotopes. Through complementary design and additional R&D, the 2nd detector could also enhance capabilities such as muon and hadron identification, as well as momentum resolution for charged particles and photons. Many of these would be synergistic with the second focus and important for processes such as coherent diffraction, DVCS on nuclei, and double DVCS. This talk will discuss some of the physics opportunities, constraints, and possible implementations for a 2nd EIC detector.
In recent years, a number of studies have explored the potential of jet observables to contribute to various aspects of the scientific mission at the future Electron-Ion Collider (EIC) and have led to the recognition that jets will play an important role at the EIC. This talk will provide an overview of jet measurements at the EIC, highlighting the ways they both complement more traditional electron-hadron scattering observables and provide unique information and capabilities. The current status of jet reconstruction using the ePIC detector model and reconstruction framework will also be discussed.
I will present a series of studies carried out by PDF groups on the impact of EIC pseudodata in constraining collinear PDFs at up to approximate N3LO in QCD. This will include the influence of inclusive EIC DIS neutral and charged current electron-proton data on the HERAPDF and MSHT global PDF determinations, as well as deuteron and positron data on CT global PDFs. For all cases studied, significant improvements in the PDF uncertainties are observed for several parton species. The consequences for LHC phenomenology will be discussed. In addition, I will outline an ongoing study into the potential of EIC data to constrain the strong coupling constant of QCD in conjunction with HERA and LHC data. These studies all serve to demonstrate the complementarity of the EIC and LHC programs for future analyses.
Exclusive C = +1 quarkonium production in high-energy electron-proton
scattering requires a C-odd t-channel exchange of a photon or three
gluons, i.e. the perturbative Odderon. The relative phase of the amplitudes
is determined by the sign of the light-front matrix element of the
eikonal color current operator $d^{abc} J^{+a} J^{+b} J^{+c}$. This is
non-vanishing only in the presence of non-Gaussian color charge
fluctuations in the proton. Model calculations predict constructive
interference of photon and three gluon exchanges and that the Odderon
dominates beyond momentum transfer $|t| ∼ 1$ GeV$^2$. Numerical predictions
for the cross sections for exclusive production of scalar, axial-vector and
tensor Chi_{c} states will be presented.
The Color Glass Condensate (CGC) effective theory and the collinear factorization at high-twist (HT) are two well-known frameworks describing perturbative QCD multiple scatterings in nuclear media. It has long been recognized that these two formalisms have their own domain of validity in different kinematics regions. In this work, we argue that a consistent matching between both frameworks, in their common domain of validity, is achieved by incorporating the sub-eikonal longitudinal momentum phase in the CGC formalism, which mediates the transition between coherent and incoherent scattering. We perform a detailed calculation and analysis of direct photon production in proton-nucleus scattering as a concrete example to establish the matching between HT and CGC up to twist-4, including initial- and final-state interactions, as well as their interferences. The techniques developed in this work can be adapted to other processes in electron-nucleus and proton-nucleus collisions, and they provide a potential avenue for a unified picture of dilute-dense dynamics in nuclear media.