The nucleon spin structure is an important aspect of hadronic physics, and spin sum rules have been extensively used to study it. We will report on the latest experimental results published on nucleon spin sum rules. The data were taken at Jefferson Lab in Hall A and B by experiments E97-110 and EG4, respectively. They covered the very low $Q^2$ domain, down to $Q^2 \sim 0.02$ GeV$^2$, Chiral...
The GlueX experiment at Jefferson Lab has collected a world-leading set of photoproduction data, which is being used to address many outstanding problems in hadronic physics. I will present the status of the search for hybrid mesons with GlueX data, including recent results on polarization observables and partial wave analyses. I will also discuss a selection of other recent results,...
In this talk, I will provide an overview of recent theoretical developments in understanding the three-dimensional momentum-space structure of hadrons.
Transverse Momentum Distributions (TMDs) are essential for describing processes like semi-inclusive deep inelastic scattering (SIDIS), Drell-Yan production, and hadron-hadron collisions at low transverse momentum, where transverse...
Super Pioneering High Energy Nuclear Interaction eXperiment (sPHENIX) is a high energy nuclear physics detector which is part of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) on Long Island, New York. sPHENIX is designed primarily to measure Quark-Gluon Plasma (QGP), produced in heavy-ion collisions at RHIC. QGP is a short-lived, hot, dense partonic medium...
Discovery of the X(3872) meson in 2003 ignited intense interest in exotic (neither qq¯ nor qqq) hadrons, but a cc¯ interpretation of this state was difficult to exclude. An unequivocal exotic was discovered in the Zc(3900)+ meson -- a charged charmonium-like state. A variety of models of exotic structure have been advanced but consensus is elusive. The grand lesson from heavy quarkonia was...
The Electron-Ion Collider (EIC) at the Brookhaven National Laboratory is a versatile machine which is designed to address some of the most profound questions about the properties of nuclear matter. To unravel the rich structure of hadrons the EIC will provide the precise imaging of the dense QCD medium inside protons and nuclei. However, understanding of the hadron structure is not possible...
Studying the in-medium stimulated effects entails improving the experimental methods to probe the confinement dynamics of quarks and gluons, the building blocks of atomic nuclei. Therefore, the deeper one looks, the more perplexing the strongly interacting particles, namely hadrons, behave. Unraveling this behavior, as described by quantum chromodynamics (QCD), the theory of strong...
Measuring parton distribution functions (PDFs) in the valence region at high Bjorken-x is one pillar of the experimental program of Jefferson Lab at 12 GeV. In this talk, I will review the status of our knowledge of polarized and unpolarized nucleon structure functions at very high x. I will especially focus on the recent “BONuS12” experiment with CLAS12 at Jefferson lab to measure the...
A priori, nothing prohibits the existence of exotic hadrons in QCD. However, for the particular case of elusive pentaquarks, more than fifty years of experimental research ended up being inconclusive, leaving the scientific community wondering if they really exist. The LHCb Collaboration announcement on the two new pentaquark states with heavy quark content in 2015 revived the interest in the...
World-record data samples collected by the BESIII detector provide an ideal laboratory for hadron spectroscopy studies. Using 10 billion event and 2.7 billion event samples collected at the $J/\psi$ and $\psi(2S)$ resonances of charmonium, respectively, detailed studies of light hadrons and charmonium decays are conducted. Scan samples above 4 GeV allow for investigations into exotic candidate...
Relativistic heavy-ion collisions produce loosely bound hadronic molecules at a rate that is surprising large, since the molecules seem to emerge from a hadron gas whose temperature is orders of magnitude larger than their binding energies. These molecules have been referred to as "snowballs in hell". Their production has been explained in terms of a novel thermodynamic variable conjugate to...
The structure of the $\Lambda(1405)$ resonance has challenged hadron physicists for more than forty years. Its structure is controversially debated as either: an antikaon-nucleon bound state, a dynamically generated baryon resembling a meson-baryon molecule, or a resonance with $\pi\Sigma$ and $\bar{K}N$ poles. Experimental results vary in line shape and peak position, depending on reaction...
Understanding the confinement dynamics of quarks and gluons, the building blocks of atomic nuclei, remains a prime challenge in modern subatomic physics.~This investigation could be carried out by studying hadronization processes, particularly in the nuclear medium, where medium-stimulated effects such as hadron attenuation and transverse momentum broadening can be probed, providing critical...
We expand upon small-$x$ helicity phenomenology by using the small-$x$ helicity evolution equations in a global analysis that now incorporates polarized proton-proton ($pp$) data in addition to the previously analyzed deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data, all at $x < 0.1$. We specifically analyze the double longitudinal spin asymmetry in single-inclusive jet...
We develop parameterizations of 8 of the lowest Born-Oppenheimer potentials for quarkonium
hybrid mesons as functions of the separation r of the static quark and antiquark sources. The
parameters are determined by fitting results calculated using pure SU(3) lattice gauge theory.
The parameterizations have the correct limiting behavior at small r, where the potentials form
multiplets...
The critical questions posed by the 2023 Nuclear Science Long Range Plan include "how are the various hadrons produced in a single scattering process correlated to one another", and "how does hadronization change in a dense partonic environment?".
The results we present in this talk on azimuthal correlations in $\pi^+\pi^-$ and $\pi^+p$ pairs measured by the CLAS collaboration at Jefferson...
A significant open question is how to bridge two disparate regimes of QCD: the high $Q^2$ regime, where perturbative QCD describes the behavior of quarks and gluons very well, and the low $Q^2$ regime, where effective theories such as Chiral Perturbation Theory are most successful at describing partonic structure. One way to study the transition between these regions is with the use of nucleon...
The Λ(1405) hyperon (JP = 1/2−), situated just below the ¯KN threshold, has been a long-standing candidate for an exotic ¯KN molecular structure. Chiral-unitary models propose that it consists of two isospin I = 0 poles with different couplings to the ¯KN and Σ0π0 systems, leading to a line shape that deviates from a relativistic Breit-Wigner distribution. The GlueX experiment at Jefferson Lab...
The abundance of exotic hadron candidates has driven a global effort to understand their emergence from hadronic interactions and QCD dynamics. The Exotic Hadron Collaboration (ExoHad) explores all aspects of exotic hadron physics, from predictions within lattice QCD, through reliable extraction of their existence and properties from experimental data, to descriptions of their structure within...
Searching for evidence of Color Transparency (CT) is a vibrant experimental effort to observe hadrons in a small neutral transverse size configuration in the nucleus. The observation of the onset of CT lies at the intersections between the quark-gluon degrees of freedom and the nucleonic descriptions of nuclei. CT is fundamentally predicted by quantum chromodynamics and is expected to be...
The nucleon electromagnetic form factors (EMFFs) are among the most basic observables sensitive to the nucleon's internal structure. However, aside from $G_M^p$, high-precision data for the nucleon EMFFs at high-Q$^2$ are scarce due to the challenges associated with such measurements. To address this, the Super BigBite Spectrometer (SBS) collaboration is currently conducting a series of...
Exploring EMC-style ratios for x>1 provides critical insights into the EMC effect. Inclusive scattering from nuclei at Bjorken x>1 and high Q2 is particularly sensitive to the distribution of high-momentum quarks, often referred to as 'superfast quarks.' These quarks, which carry momentum exceeding that of a nucleon, are linked to the short-distance structure of nuclei. This region presents a...
Multiple approaches attempt to describe hard and semi-hard scattering processes in p+A-style collisions. One approach is based on leading-twist pQCD in a collinear factorization picture, where all initial and final state effects on hard processes are included within a set of nuclear parton density functions (nPDFs) universal in x and Q^2. Other approaches are based on a dynamical description...
Generalized Partons Distributions (GPDs) give a 3-dimensional description of the structure of the nucleon, and give insights into the origin of its spin and the forces at play within it. The study of the Deeply Virtual Compton Scattering (DVCS) reaction with both polarized protons and neutrons is important for the complete extraction of GPDs and of their flavor dependency. Part of the Run...
Nuclear Short Range Correlations (SRCs) are pairs of nucleons that exist at short relative distances and high relative momenta within the nucleus. These SRC pairs significantly impact nuclear structure and have been extensively studied using hard quasi-elastic electron-scattering data. Interpretation of these data rely on our understanding of the reaction mechanisms in electron scattering as...
Hadronic resonances are emergent phenomena of Quantum Chromodynamics at intermediate energies. Almost all resonances decay not only to two, but also to three or more particles. Parametrizing three-body dynamics in terms of unitary coupled-channel amplitudes is, therefore, a prerequisite for the extraction of resonances from experiment and also from finite-volume lattice QCD spectra. In the...
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...
Cascade hyperons, despite being discovered over half a century ago, remain considerably less studied compared to the non-strange $\Delta$ and $N$ baryons. This disparity is primarily due to the energetic challenges associated with producing two strange quarks. The objective of this analysis is to provide the first cross-section measurements for the ground state cascade, $\Xi^-$, using electron...
We will discuss our experimental projects for JLab Hall C to measure novel Compton-like reactions (Timelike Compton Scattering TCS, Double Deeply Virtual Compton Scattering DDVCS) in order to improve our knowledge on Generalized Parton Distributions (GPDs) beyond what is currently accessed from DVCS (Deeply Virtual Compton Scattering). GPDs can lead to interpretation such as tomographic views...
The nucleon-nucleon interaction at short distances is the primary mechanism responsible for generating high-momentum components in nucleon momentum distributions. The isospin structure and abundance of 2-nucleon short-range correlations (2N SRCs) have been studied in detail in both light and heavy nuclei. Additionally, theoretical models predict that 3N SRCs will emerge and become dominant at...
We are currently developing at Virginia Tech a new muon detector aimed at detecting and discriminating muon pairs in exclusive reactions such as Double Deeply Virtual Compton Scattering or J/psi production. We developed a DAQ system and a first prototype system in our lab. In parallel, we are working on simulations to obtain the best design, able to handle high rate and properly separate muons...
The chiral magnetic effect (CME) in heavy-ion collisions reflects the local violation of ${\cal P}$ and ${\cal CP}$ symmetries in strong interactions and manifests as electric charge separation along the direction of the magnetic field created by the wounded nuclei. The experimental observables for the CME, such as the $\gamma_{112}$ correlator, the $R_{\Psi_2}(\Delta S)$ correlator, and the...
The EMC effect, an observed difference in the partonic structure of bound versus free nucleons, remains unexplained forty years after its initial discovery. Naively, quark-gluon confinement and the scale separation between QCD dynamics (GeV) and internucleonic interactions (MeV) would imply that the two descriptions are largely independent of one another. Surprisingly, the EMC effect indicates...
This presentation covers recent advancements in the refined simulations of double pion electroproduction for CLAS22. Double pion production provides a valuable probe of baryon structure, requiring accurate simulations for proper interpretation of experimental data. The presentation addresses the feasibility of extending the kinematic coverage beyond CLAS12, discussing resolution and acceptance...
The modification of bound nucleon structure function in nuclei, known as the EMC Effect, was first observed over 40 years ago through Deep Inelastic Scattering (DIS) ratios comparing deuterium to other nuclei. Despite extensive study, the underlying mechanism behind this effect remains unresolved. A prominent hypothesis attributes the EMC Effect primarily to the modification of high-virtuality...
The Continuous Electron Beam Accelerator Facility, CEBAF, at the Thomas Jefferson National Accelerator Facility has been conducting world class nuclear physics experiments for nearly thirty years. I will give an overview of the current experimental program as well as an overview of the machines tentative schedule for the next several years. I will also present possible future machine...
Timelike Compton Scattering (TCS) is the timelike equivalent of Deeply Virtual Compton Scattering (DVCS) for which many experiments have been conducted at Jefferson Lab over the past 20 years in order to access Generalized Parton Distributions (GPDs) and information about the 3D structure of the nucleon. TCS is the golden channel to complement DVCS measurements and perform universality studies...
Understanding the origin of the proton's mass is a fundamental question in nuclear physics. The proton’s three valence quarks account for only a small fraction of its total mass, with the majority arising from the strong force, mediated by gluons.
Recent experiments studying near-threshold J/ψ production at Jefferson Lab have provided new insights into the proton's mass distribution. I will...
Ultra-peripheral collisions (UPCs) at the Relativistic Heavy Ion Collider and the Large Hadron Collider offer a unique laboratory for exploring the interplay between quantum electrodynamics and quantum chromodynamics in the presence of intense electromagnetic fields. These collisions, characterized by impact parameters exceeding the sum of the radii of the colliding nuclei, generate powerful...
The overarching goal in the realm of strong QCD physics is to gain a fundamental understanding of the nature of hadronic matter and its interactions. This involves exploring how Quantum Chromodynamics (QCD) manifests itself on the scales relevant to the formation of hadrons. Identifying the underlying symmetries and degrees of freedom that dictate the observed properties of hadrons is crucial...
CD is a difficult theory of hadrons because it is described entirely unobservable partons, the quarks and gluons. In order to access parton distributions, hadronic observables such as experimental cross sections or lattice QCD matrix elements must have factorization approximations separated hadronic and partonic distance scales. These observables are sensitive to different regimes in momentum...
In this talk, we will present the recent results from the Relativistic Heavy Ion Collider Beam Energy Scan II, with a special focus on the exploration of the QCD phase structure.
In ultrarelativistic heavy ion collisions, an exotic phase of matter known as the quark-gluon plasma (QGP) is created. The QGP is a thermodynamic system characterized by extremely high temperatures and energy densities, where quarks and gluons can move beyond the confines of nucleons. Recent years have seen a multitude of studies uncovering many intriguing phenomena of QGP. Jets, which are...
In this talk, we will review recent progress in utilizing energy-energy correlators to study hadron structure. Specifically, we will explore how energy-energy correlators with azimuthal angle dependence can be employed to investigate the transverse momentum-dependent (TMD) structure of hadrons and the phenomenon of small-$x$ gluon saturation. Additionally, we will discuss their application in...
Nuclear and high-energy physics facilities, such as CERN, Jefferson Lab, RHIC, and the forthcoming EIC, are producing exabytes of data. This unprecedented amount of data promises to provide a better understanding of QCD in the nonperturbative regime. However, extracting the required information is an extremely challenging task, as there is no available QCD analytic solution to interpret data....
Jet substructure is a powerful tool for performing fundamental QCD tests in elementary particle collisions and offers unique insight into the microscopic structure of the QGP in heavy-ion collisions. Defined as the energy-weighted cross section of particle pairs inside jets, the two-point energy-energy correlator (EEC) is a novel jet substructure observable probing the correlation of energy...
The upcoming EIC will allow us to study in depth the three-dimensional tomography of hadrons via Generalized Parton Distributions (GPDs). Recently, the 𝑥-dependence of GPDs have been found to be extracted from the lattice utilizing matrix elements of nonlocal operators. In this presentation we discuss results on the transversity GPDs utilizing novel theoretical developments of lattice QCD to...
The High-Acceptance Di-Electron Spectrometer (HADES) operates at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, using pion, proton, and heavy-ion beams provided by the SIS-18 synchrotron [1]. In February 2022, the HADES Collaboration measured proton-proton collisions at 4.5 GeV momentum using the upgraded setup as part of the FAIR-Phase0 program.
One of the key objectives of...
This talk presents the first measurement of low-transverse-momentum ($p_T$) charged-hadron distributions in pseudorapidity and azimuthal angle, relative to the momentum direction of $Z$ bosons, in lead-lead ($\mathrm{PbPb}$) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_\mathrm{NN}} = 5.02$ TeV. The analysis uses PbPb data from 2018 with an integrated luminosity of $1.67...
SpinQuest is the Fermilab fixed-target Drell-Yan (DY) experiment that aims to measure the sea-quark Sivers functions by impinging a 120 GeV unpolarized proton beam on transversely polarized ammonia, NH$_3$, and deuterated ammonia, ND$_3$, targets. In this measurement, the DY process also offers clean access to the transversity distribution, $h_1(x)$, quantifying the probability of scattering...
We present recent results and future outlook for gluon parton distributions from lattice QCD, focusing primarily on the pion and nucleon gluon parton distribution functions (PDFs). The nucleon gluon PDF is a crucial input to the prediction of rare physics processes such as Higgs and $J/\psi$ production and beyond the standard model physics. The pion gluon PDF is expected to hold clues about...
The X17 anomaly refers to a bump seen in the pair production spectrum of the decay to ground state of excited Be8 nuclei. This was first observed in 2015 at the ATOMKI Van de Graaf generator and was repeated using He4 and C12. The most prominent explanation is a hidden-sector boson that mediates a “fifth force” that couples to dark matter and has small kinetic mixing with the electromagnetic...
For the CLAS Collaboration
As part of the efforts to gain more insights into the bound nucleon structure and the associated in-medium modifications that led to the still-to-be-unraveled EMC (European Muon Collaboration) effect, novel approaches can be deployed using, for example, the deeply virtual Compton scattering (DVCS) process to probe the partonic structure of light nuclei, such as 2H...
We calculate the subeikonal corrections to the differential cross-section of inclusive and incoherent diffractive dijet production in DIS using the background field method. In contrast to the existing studies, we perform the calculation without assuming finite support of the background field. The next order corrections not only arise from the expansion of the phases, which accounts for the...
Due to the non-perturbative nature of QCD in the present low temperature universe, the vacuum has hidden underlying structures. We are making experimental studies to study the structure through precision spectroscopy of meson-nucleus bound systems. Recently we reported the first quantitative evaluation of the chiral condensate in the nuclear matter observed in the spectroscopy of pionic atoms....
In this presentation, I will show how the difference of interacting and non-interacting integrated two-particle correlation functions in finite volume is related to infinite volume scattering phase shift through an integral weighted by a factor exp(-Et). The difference of integrated finite volume correlation functions converge rapidly to its infinite volume limit as the size of periodic box is...
The ePIC experiment at the upcoming Electron-Ion Collider (EIC) is advancing toward compute-detector integration with seamless data processing from detector readout to analysis. This paradigm shift in data processing is driven by streaming readout and AI technologies.
Streaming readout captures every collision signal, including background events, ensuring no information is lost. This...
Artificial intelligence and machine learning techniques have gained increasing attention in recent years as powerful tools for advancing data analysis and simulations across various fields of physics. Among these, generative models are notable for their ability to create complex data distributions, with Generative Adversarial Networks (GANs) already showing promise in reducing the...
The precise mechanism underlying spin-flavor symmetry breaking in QCD is unknown but is illuminated by the behavior of high momentum quarks in the nucleon. Conventionally, high partons have been studied by extracting the neutron-to-proton structure function ratio via fits to nuclear DIS data. However, these fits rely on model-dependent, theoretical descriptions of nuclear effects.
The...
In this paper, we investigate an inflation scenario and dark energy in a scaled gravity, R + βR where β is a dimensionless gravity parameter, with a kinetic term. To reduce the associated moduli space, we implement such a parameter in a specific scalar potential given by V (ϕ) = M4(1 − (ϕ μ)β). By computing the relevant cosmological observables including the spectral index ns and the...
Uncertainty quantification (UQ) plays a crucial role in the predictive power of nonperturbative quantum correlation functions at high precision. My research explores new approaches to UQ in the context of parton distribution functions (PDFs), using machine learning techniques to map between observables and underlying theoretical models, and navigate the complex parametric landscape of...
The hadron spectrum offers deep insights into the strong force, the origin of hadronic mass, quark confinement, and the transition from quarks and gluons to observable particles. While the quark structure of hadrons is well understood, most of their mass arises from the binding force rather than the quarks themselves — this is a largely uncharted territory whose exploration has been attracting...
A TeV muon-ion collider could be established if a high energy muon beam that is appropriately cooled and accelerated to the TeV scale is brought into collision with a high energy hadron beam at facilities such as Brookhaven National Lab, Fermilab, or CERN. Such a collider opens up a new regime for deep inelastic scattering studies at unprecedented small Bjorken-$x$ and high Q$^{2}$, as well as...
In ultraperipheral heavy-ion collisions (UPCs), vector meson photoproduction, e.g. $\rho^{0}$ and $J/\psi$, has been considered one of the most sensitive probes for studying the gluonic structure in heavy nuclei. The linear polarization of the photons involved in these processes can help to image the nucleus through the spin interference effect in vector meson photoproduction. Many efforts...
The system of η and η′ offers a flavor-conserving laboratory to test the low-energy QCD and to search for new physics Beyond the Standard Model. The symmetry properties of QCD at low-energy, such as the chiral symmetry or the axial anomalies, are manifested in the decays of η and η′. Thus, a study of η/η′ will yield light on our understanding of the origin and the dynamics of QCD...
The shapes of colliding nuclei influence flow patterns in heavy-ion collisions due to hydrodynamic responses to collision geometry. We performed simulations to study the impact of nuclear structure on anisotropic flow ratios in Pb+Pb and Xe+Xe collisions at the LHC. Our findings show these ratios are significantly affected by nuclear structure, offering a new method to probe deformed nuclear...
Understanding the dynamics of QCD at high energy or small Bjorken x is crucial for describing gluon saturation and non-linear interactions within hadronic wave functions. This regime, characterized by high gluon densities, pushes QCD into a dense domain where standard techniques are insufficient. Evolution equations like the JIMWLK equation capture this behavior. While the leading-order (LO)...
At high energy, the fundamental description of matter (Quantum Chromodynamics or QCD) is currently only directly applicable to specific regimes, leaving large portions of the QCD phase diagram uncharted, especially around the regime relevant for neutron stars. To bridge different regimes, the MUSES collaboration has built a cyberinfrastructure that provides descriptions of matter based on...
Ultrarelativistic isobar collisions serve as a powerful tool for probing nuclear structures. These high-energy collisions are typically described by a hydrodynamic expansion, preceded by a pre-thermal equilibrium phase. However, due to the computational complexity of hydrodynamic simulations, studies of isobar nuclear structures often rely on geometrical estimators, such as eccentricities,...
The study of $\rm{J}/\psi$ photoproduction in ultra-peripheral collisions (UPCs) offers a powerful probe of gluon dynamics in heavy nuclei. In UPCs, photons can interact with the nucleus coherently (involving the entire nucleus) or incoherently (with individual constituents). While coherent processes provide insight into the average gluon density, incoherent photoproduction is uniquely...
The implementation of general principles, like analyticity and unitarity, can help to constrain the determination of hadronic properties from lattice QCD (LQCD).
We present the LQCD calculation of the pion vector form factor over spacelike and timelike kinematics, with a pion mass of approximately $284$ MeV.
We go beyond the elastic timelike region, and implement for the first time the...
Building a description of nuclear matter valid at arbitrary thermodynamic conditions is a difficult task, even when restricted to the zero temperature limit. In this talk, we will discuss how to build a Neutron Star using three different Equation of State models in their specific range of validity using the MUSES framework: Crust Density Functional Theory valid starting at low densities,...
Nuclear spectroscopy with heavy ion beams and fixed targets has emerged as a powerful tool for studying sub-atomic nuclei with strangeness, known as hypernuclei. Recent experiments using high-energy heavy ion beams have challenged the current understanding of light hypernuclei [1,2,3,4,5,6,7,8], particularly the hypertriton which is a subject of ongoing debate in the field, often referred to...
The first excited state of the nucleon dominates many nuclear phenomena at energies above the pion-production threshold and plays a prominent role in the physics of the strong interaction. The study of the N to $\Delta$ transition form factors (TFFs) allows to shed light on key aspects of the nucleonic structure that are essential for the complete understanding of the nucleon dynamics. In this...
We present a comprehensive study of bottomonium ($\Upsilon(1S)$, $\Upsilon(2S)$, and $\Upsilon(3S)$) suppression in minimum-bias proton-Lead ($p$-Pb) collisions at 5.02 and 8.16 TeV. Our approach accounts for both cold nuclear matter (CNM) effects (nuclear parton distribution function (nPDF) effects, coherent energy loss and momentum broadening), and hot nuclear matter (HNM) effect due to the...
The photoproduction of vector mesons off the proton serves as a crucial probe of the gluon content within the nucleon. Near-threshold J/psi photoproduction provides a unique opportunity to investigate the Gravitational Form Factors of gluons, which are related to the mass, pressure, and force distributions within the proton. Furthermore, this reaction allows for the exploration of exotic...
I will report on our current progress in phenomenological extraction of Generalized Parton Distributions (GPDs) utilizing neural networks and stochastic gradient descent optimization.
The emergence and evolution of collective behavior in small collision systems remains a key area of interest in high-energy nuclear physics. To understand how collectivity evolves with system size RHIC has conducted a dedicated small system scans, including He$^3$+Au, d+Au, and p+Au collisions.
In 2021, the STAR collaboration expanded the scan by introducing a symmetric yet small system...
A number of new four-quark states containing from one to four $c$ or $\overline c$ quarks have been observed recently. Many of these new states have been discovered at the LHC. The production of these states via intrinsic charm in the proton is investigated. The tetraquark masses obtained in this approac agree well with the measured masses [1]. These calculations can provide some insight...
J/ψ near-threshold photoproduction plays a key role in the physics program at the Thomas Jefferson National Accelerator Facility (JLab) 12 GeV upgrade due to the wealth of information it has to offer. Near threshold, J/ψ photoproduction proceeds through the exchange of gluons in the t-channel and is expected to provide unique insight about the nucleon gluonic form factors and the nucleon mass...
In this work, we present updates of the progress towards the first simultaneous extraction of unpolarized collinear and transverse momentum dependent (TMD) parton distribution functions (PDFs) in the proton. The TMD factorization is conveniently formulated in $b_T$-space, which is the Fourier conjugate to the intrinsic transverse momentum of quarks within the proton, $k_T$. In the small-$b_T$...
Critical points are categorized based on the number of relevant variables. The standard critical point in systems like the Ising model involves two relevant variables, namely temperature and external magnetic field. In contrast, a tricritical point is characterized by four such variables. The protocritical point, widely known as the Yang-Lee edge singularity (YLE), is the simplest form of...
One of the best ways to understand hadronization in QCD is to study the production of quarkonium. The color evaporation model (CEM) and Nonrelativistic QCD (NRQCD) can describe production yields rather well but spin-related measurements like the polarization are stronger tests. In this talk, we will present the first expansion of the improved CEM into electron-proton collisions, and the...
Double parton scattering in p+p and p+A collisions is described by double parton distribution functions (dPDFs), a joint distribution over two partons. dPDFs differ from a product of single-parton distribution functions (PDF) since they encode parton correlations. We compute the double quark density matrix and dPDF from a simple three-quark model proton light-cone wave function. We then...
SpinQuest is the Fermilab's high-luminosity Drell-Yan experiment that aims to explore the interaction of 120 GeV proton beam with transversely polarized ammonia (NH$_3$), and deuterated ammonia (ND$_3$) targets to probe the Sivers functions of light quark flavors in the nucleon sea. A non-vanishing sea quark Sivers functions provide evidence of their orbital angular momentum, which would...
The dominant interaction between a heavy quark and antiquark at low energy is described through the static potential. The real part of the potential becomes screened with a screening mass proportional to the temperature, and the imaginary part of the potential gives bound-states a non-zero width. As the temperature increases bound-states can disappear either because they are not supported by...
The transverse single-spin asymmetry (TSSA) measures the asymmetry in particle production relative to the plane defined by the transverse spin axis and the momentum direction of a polarized hadron. TSSAs have emerged as a powerful tool for exploring Quantum Chromodynamics (QCD), offering insights into the dynamics of initial-state hadrons and the hadronization process. In J/ψ production, which...
We describe numerical simulations of stochastic fluid dynamics near a critical point in the Ising universality class. This theory is known as model H, and is expected to govern universal dynamics in the vicinity of a possible critical endpoint in the QCD phase diagram. We verify dynamic scaling near the critical point of a two and three-dimensional fluid and extract the associated critical...
High-energy collisions between unpolarized electrons and nucleons allow for the probing of the internal structure of nucleons (protons and neutrons). This can be accomplished through the use of inclusive deep inelastic scattering (DIS), where only the scattered electron is detected, or semi-inclusive deep inelastic scattering (SIDIS), where also another final-state particle is detected. If the...
In this talk, we will summarize the goals of the workshop held at Stony Brook University (CFNS) in January 2025, which focused on advancing our understanding of cold nuclear matter (CNM) effects in hadron-nucleus (h+A) collisions. We will explore the challenges of applying perturbative Quantum Chromodynamics (pQCD) to h+A collisions, particularly the complexities arising from CNM effects such...
Measuring jet substructure at the Large Hadron Collider provides exciting new opportunities to study detailed aspects of QCD dynamics. Comprehensive jet substructure measurements in proton collisions have played a critical role in mapping the multi-scale evolution of jets. Jet substructure measurements in heavy flavor jets have even led to the direct observation of the suppression of collinear...
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...
Exclusive vector-meson production in e+A collisions has been suggested as a probe to analyze the distribution of gluons within the nucleus. However, the Good-Walker paradigm implies that coherent exclusive events probe the spatial distribution of the nucleons, whereas incoherent exclusive interactions are sensitive to event-by-event fluctuations within the nucleus. Consequently, any photons...
In this talk, I will report some recent progress in extracting the gluonic gravitational form factors (GFFs) from near threshold heavy quarkonium productions. Particularly, I will discuss the effect of the next-to-leading order (NLO) corrections on the extraction of the GFFs, where the singlet quark contribution will also emerge. With the NLO corrections, I will remark on the theoretical...
Backward, or $u$-channel, production of mesons in $ep$ collisions results in a nearly-stopped proton and a meson with a large forward momentum. In conventional (forward, $t$-channel) production, the momentum transfer from the proton to the meson is small and is modeled by pomeron-exchange trajectories. These $t$-channel production cross sections can be transformed into target density...
The study of the three-dimensional (3-D-longitudinal and transverse-momentum) imaging and spin structure of the nucleon emerged from studies of power-suppressed/next-to-leading power (NLP) azimuthal modulation and transverse spin asymmetries in semi-inclusive deep inelastic scattering (SIDIS) experiments. In this talk I will present our latest work on establishing TMD factorization at next to...
In the aftermath of a high energy non-central heavy-ion collision, it is expected that along a quark-gluon plasma (QGP) a very strong electromagnetic field is produced. To characterize the strength of such a field, it has been theorized that it can induce measurable effects on the width and leptonic invariant mass of the Z-boson, with the effect being maximal for semi-central collisions. We...
Directed flow of particles is an important feature seen in heavy-ion collisions and is a
sensitive probe of the equation of state (EoS) of the matter produced in the collisions.
Model calculations have also predicted that directed flow could be a sensitive probe of the
softening of the EoS associated with a first order phase transition. Directed flow of protons
and anti-protons are also of...
Recent advancements in both theoretical frameworks and experimental methodologies have significantly enhanced our understanding of the internal mechanical properties of nucleons, particularly the role of gluonic contributions. Central to this investigation are the gravitational form factors, which encapsulate the nucleon’s energy, momentum, pressure, and shear distributions. These form factors...
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...
The proposed Electron-Ion Collider (EIC) will utilize high-luminosity high-energy electron+proton ($e+p$) and electron+nucleus ($e+A$) collisions at different center of mass energies to solve several fundamental questions in the nuclear physics field. Due to their high masses ($M_{c,b} > \Lambda_{QCD}$), heavy quarks are produced early in hard partonic scatterings and their flavors are...
The Relativistic Heavy Ion Collider (RHIC) has been in operation since 2001, contributing significantly to the study of strong interactions and nuclear matter under extreme conditions. The PHENIX experiment, operated from 2001 to 2016, has collected a comprehensive dataset that continues to yield impactful results with heavy flavor probes. These measurements have provided critical insights...
Currently, the nature of the baryon number carrier remains debated. Although it is conventionally assumed to be carried by quarks, an alternative model suggests that the baryon number is instead carried by a Y-shaped gluon configuration called the baryon junction. This has significant ramifications for baryon emission at mid-rapidity in nuclear collisions. In this work, we accurately extract...
Over the last two decades, the PHENIX experiment has utilized the polarized proton collisions delivered at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory to study spin structure and dynamics in high energy nuclear physics. Measurements of longitudinal spin asymmetries in direct photons and light mesons revealed the important contribution of gluon polarization to...
Relativistic ion collisions quickly form a droplet of quark–gluon plasma (QGP) with a remarkably small viscosity. This smallest and hottest fluid on earth can only be understood by studying a multitude of physical stages, including a far-from-equilibrium colliding stage, a stage described by viscous relativistic hydrodynamics and as a gas of hadrons that can finally be detected by experiments...
We will address various aspects of the very rich chiral and partonic structure of strongly interacting systems such as the nucleon. One example are the (generalized) polarizabilities of the nucleon, which are largely governed by chiral dynamics. As far as the partonic structure of the nucleon is concerned, we will cover the non-trivial universality of transverse-momentum dependent...
The talk will review the recent series of Hall A experiments at Jefferson Lab to measure the elastic electric and magnetic form factors of the proton and neutron to a large $Q^2$ which would doubled or tripled the $Q^2$ range of previous precision measurements. Two large acceptance spectrometers were used so that the form factors could be measured with high precision. From 2021 to 2024, the...
Mapping the 3D structure of the proton in terms of its spinning quark and gluon constituents is one of the main goals in current hadronic physics. Generalized parton distributions can provide part of the solution, through Fourier transformation of the single particle spatial density of quarks and gluons with a given longitudinal momentum fraction, x, while a fuller dynamical picture of the...
Strong highly boosted electromagnetic fields are equivalent to a flux of quasi-real photons, such as the fields created in ultrarelativistic heavy ion colliders like the Large Hadron Collider (LHC) and the Relativistic Heavy Ion Collider (RHIC). The copious flux of photons allows, for the first time, detailed studies of high-energy photon-nucleus collisions which at the LHC can reach center of...
