The 11th workshop of the APS Topical Group on Hadronic Physics

Mar 14, 2025, 7:00 AM → Mar 16, 2025, 8:15 PM US/Pacific

Anaheim Convention Center

Bernd Surrow (Temple University), Bjoern Schenke (Brookhaven National Lab)

Dear participants, speakers, session chairs,

thank you all for coming to the workshop and for sharing your latest results with the GHP community! You made it a successful meeting with great talks and discussions.

Stay tuned for time & location of the next edition, GHP2027.

 

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The 11th biennial workshop of the APS Topical Group on Hadronic Physics (GHP2025)  provides great opportunities for nuclear and particle physicists to meet and discuss their common interests in hadronic interactions.

The workshop precedes the 2025 Global Physics Summit (March 16-21, 2025)  of the American Physical Society and will take place at the same location.

 

GHP 2025 - Call for Abtracts.pdf

GHP2025 - First Circular.pdf

GHP2025-InstructionsSessionChairs.pdf

GHP2025 - Second Circular.pdf

GHP2025-Sessions-Chairs-TechHelp.pdf

map.pdf

Poster_GHP2025.jpeg

Poster_GHP2025.pdf

DoorSigns

• GHP2025-DoorSign-252A-Friday.pdf
• GHP2025-DoorSign-252A-Saturday.pdf
• GHP2025-DoorSign-252A-Sunday.pdf
• GHP2025-DoorSign-252B-Friday.pdf
• GHP2025-DoorSign-252B-Saturday.pdf
• GHP2025-DoorSign-252B-Sunday.pdf
• GHP2025-DoorSign-252C-Friday.pdf
• GHP2025-DoorSign-252C-Saturday.pdf
• GHP2025-DoorSign-252C-Sunday.pdf
• GHP2025-DoorSign-255B-Friday.pdf
• GHP2025-DoorSign-255B-Saturday.pdf
• GHP2025-DoorSign-255B-Sunday.pdf

Friday, March 14

Registration & Welcome

1 Registration

2 Welcome

Speaker: Bjoern Schenke (Brookhaven National Lab)

Schenke-GHP-Welcome.pdf

Plenary Session - Room 255B: I (Chair: Bjoern Schenke)

Convener: Bjoern Schenke (Brookhaven National Lab)

3 Nucleon spin structure in the strong QCD regime (2023 GHP Fellow)

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 Effective Field Theory ($\chi$EFT) is applicable, thereby providing a test of its predictions. While some of the measurements agree with the state-of-the-art $\chi$EFT theoretical predictions, others are in tensions, including $\delta_{LT}^n(Q^2)$ for which $\chi$EFT prediction was expected to be robust. This suggests that $\chi$EFT does not yet consistently describe nucleon spin observables, even in the very low $Q^2$ domain covered by the experiments.

Speaker: Alexandre Deur (Thomas Jefferson National Accelerator Facility)

GHP25_Deur.pdf

4 Hadron spectroscopy with GlueX

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, including new measurements of charmonium production near-thresholds which have implications for the study of nucleon structure and the search for the photoproduction of heavy pentaquark states.

Speaker: Sean Dobbs (Florida State University)

sdobbs_GHP2025_GlueX.pdf

5 Recent Phenomenological Studies of 3D Momentum-Space Hadron Structure

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 dynamics play a crucial role.
I will present the latest global fits for unpolarized TMDs and discuss the different phenomenological frameworks used to extract these distributions from experimental data, highlighting both the challenges and successes of current approaches. Additionally, I will explore the incorporation of neural networks in TMD analyses, discussing how the flexibility of machine learning techniques can enhance our ability to model the non-perturbative part of TMDs.
Building on these developments, significant advancements have also been made in recent years in extracting polarized TMDs, like the Sivers function and the helicity TMD, from experimental data. These advancements deepen our understanding of spin-dependent phenomena and the internal spin structure of hadrons, bringing us closer to a comprehensive picture of hadron dynamics in momentum space.

Speaker: Chiara Bissolotti (Argonne National Laboratory)

GHP25_Bissolotti.pdf

6 First year(s) results from sPHENIX

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 which evolves similar to a liquid with near zero viscosity. The QGP is studied via the statistical properties of the bulk hadrons produced shortly after it expands and cools as well as internally generated probes produced from out-of-equilibrium high momentum transfer partonic scatterings at early times within itself. In particular, these hard scatterings produce collimated sprays of hadrons (jets) and high momentum heavy flavor hadrons which sPHENIX uses to probe the inner workings of the QGP. This talk will give an overview of the sPHENIX detector as well as present preliminary results from its inaugural year of physics data taking with \sqrt{s} = 200 GeV proton-proton collisions.

Speaker: Charles Hughes (Iowa State University)

sPHENIX_first_years_results_Charles_Hughes_draft6.pdf

10:30 AM Coffe Break

Plenary Session - Room 255B: II (Chair: Bernd Surrow)

Convener: Bernd Surrow (Temple University)

7 Experimental Road to a Charming Family of Tetraquarks ... and Beyond

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 that heavy quarks bring clarity. Thus, the recently reported triplet of all-charm tetraquark candidates -- X(6600), X(6900), and X(7100) -- decaying to J/ψJ/ψ is a great boon, promising important insights. We review some history of exotics, chronicle the road to prospective all-charm tetraquarks, discuss in some detail the divergent modeling of J/ψJ/ψ structures, and offer some inferences about them. These states form a Regge trajectory and appear to be a family of radial excitations. A reported, but unexplained, threshold excess could hint at a fourth family member. We close with a brief look at a step beyond: all-bottom tetraquarks.

Speaker: Kai Yi (Nanjing Normal university)

GHP2025.pdf

8 EIC Theory Overview

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 without unambiguous theoretical interpretation of the experimental results. This calls for appropriate developments in theory to be on par with experimental advances at the EIC. During the last years, there has been a lot of progress in this direction, especially in terms of better understanding of deep relations between different theoretical methods and frameworks. In my talk, I will give an overview of the recent developments in theoretical understanding of the fundamental questions to be addressed at the EIC such as spin and mass structure of the proton, three-dimensional tomography, and the gluon saturation at small x.

Speaker: Andrey Tarasov (North Carolina State University)

GHP_2025_Tarasov.pdf

9 Anticipated First Results from the Electron Ion Collider

The Electron-Ion Collider (EIC) is poised to address fundamental questions in nuclear science, as outlined by the National Academy of Science Report and detailed in the Yellow Report. Central to its mission is the understanding of nucleon structure by disentangling the contributions of quarks, gluons, and their orbital angular momentum. The EIC will allow us to determine how much of the mass of visible matter emerges from quark-gluon interactions, how these interactions dynamically originate within Quantum Chromodynamics (QCD), and the connection of these phenomena to confinement. Additionally, the EIC will probe how confined hadronic states emerge from quarks and gluons and investigate the behavior of gluon density in nuclei, including potential saturation effects. The early science program is designed to leverage the collider’s versatile beam capabilities, featuring 5 – 10 GeV polarized electrons, 100 – 250 GeV polarized protons, and 100 GeV per nucleon nuclear beams. The initial program will map the out nucleon and nuclei structure from high to low x, including the spatial and momentum structure of nucleons and nuclei in three dimensions. This talk will outline the initial commissioning plan, and the EIC Phase 1 early science program which will span the first five years of physics operation. The ability to measure key observables, such as nuclear parton distribution functions.

Speaker: Rosi Reed (Lehigh U)

RReedGHP2025v1.pdf

12:30 PM Lunch Break

Parallel Session - Room 252A: Hadrons I (Chair: Michael Doring)

Convener: Michael Doring (George Washington U and Jefferson Lab)

10 Recent results on hadronic spectroscopy at BESIII

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 charmonium-like XYZ states, the structure of which may be probed through careful study of their production mechanisms and decays. In this talk, I will explore these topics by providing an overview of some of the recent results of the BESIII hadron spectroscopy program.

Speaker: Joshua Jackson (Indiana University)

BESIII_GHP2025_Mar14.pdf

11 Λ(1405) and Λ(1520) Line Shape Studies using GlueX Phase I Data

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 provides a unique opportunity to study this phenomenon using the reaction γp → K+Λ(1405), followed by Λ(1405) → Σ0π0 and Λ(1405) → pK−. Utilizing data from the first phase of GlueX, with a photon beam energy range of 6.5–11.6 GeV incident on a liquid hydrogen target, the highest-ever statistics for this state have been achieved.

To benchmark our results, we compare them to the nearby Λ(1520) hyperon
(JP = 3/2−), a conventional quark-model state. Published GlueX results for the pK− decay mode of the Λ(1520) have been refined with additional analyses to extract its total cross-section. A novel approach of joint fits to the mass distributions of both hyperons is employed to disentangle overlapping features, particularly where the Λ(1405) tail contributes under the Λ(1520). This comprehensive study provides new insights into the exotic structure of the Λ(1405) and its implications for hadronic physics.

Speaker: Sean Dobbs (Florida State University)

sdobbs-GHP2025-Lambda.pdf

12 Recent GW activity in pion photoproduction experiments and analysis within the SAID Framework

The George Washington University has been involved in experimental, theoretical, and phenomenological activities in the field of hadron spectroscopy for several decades; each of these activities complement the others. Experimental efforts have concentrated on the A2 experiment at Mainz, as well as the CLAS and GlueX experiments at Jefferson Lab. The interpretation of these new data has been greatly aided by the SAID Partial Wave Analysis ramework, which has been hosted at George Washington since 1998 when it was transitioned from Virginia Tech. This framework uses a coupled-channel analysis to fit parameterized Chew-Mandelstam K matrices to tens of thousands of data points in dozens of observables. The solutions have been used, in comparison with other partial-wave analyses to characterize the impact of new data. In this talk, I will give an overview of the most recent experimental results in pion photo-production from both the proton and neutron, including our recent measurement of the E asymmetry for 𝛾𝑝 → 𝜋0𝑝 measured in the FROST experiment, as well as our latest SAID solutions updated for these data. I will also give an outlook on upcoming results and new experimental activities.

Speaker: Bill Briscoe (GWU)

Anaheim.pdf

Anaheim.pptx

13 Study of superfast quarks using Jefferson Lab 11 GeV data

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 promising opportunity to investigate the role of quark degrees of freedom in nuclear structure. The 12 GeV data from Jefferson Lab enables a more precise study compared to the 6 GeV data, the maximum energy achievable before the upgrade, as the higher Q2 values enhance the dominance of deep inelastic scattering (DIS) while suppressing quasi-elastic contributions

Speaker: Mr sebastian moran (UCR)

GHP-sebastianMoran.pdf

Parallel Session - Room 252B: Electroproduction from nuclear targets I (Chair: Jackson Pybus)

Convener: Jackson Pybus (LANL)

14 Color Transparency Studies via \rho$^0$ Electroproduction off Nuclei at Jefferson Lab

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 interactions, could rely on intrinsic QCD phenomena such as Color Transparency, in which the produced small-size configurations propagate almost intact in the nucleus due to the suppressed interactions with the surrounding color field. The new high-momentum transfer CT experiment accumulated data in fall 2023 using the CLAS12 detector, housed in Hall B at Jefferson Lab, and various nuclear targets ranging from deuterium to tin. In this talk, I will briefly describe my Ph.D. project and summarize the ongoing calibration and analysis efforts to extract its preliminary nuclear transparency results.

Speaker: Matthew Maynes (Mississippi State University)

APS_GHP_2025_Matthew_Maynes_2.pdf

15 Probing Hadronization Dynamics via $\Lambda$~SIDIS Production off Nuclei

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 insights into hadronization stages and thus the associated time-distance scales. In this talk, I will report on color propagation and hadron formation studies conducted at Jefferson Lab Hall B in spring 2024, deploying the CLAS12 detector and a dual-target assembly consisting of a liquid deuterium target in series with one of the five solid foils, carbon, aluminum, copper, tin, and lead. I will also discuss ongoing analysis efforts to extract preliminary results of my Ph.D. project investigating the Semi-Inclusive Deep Inelastic Scattering of $\Lambda$ hyperons off nuclei in a broad kinematical range that grants access to production in both forward and target fragmentation regions.

Speaker: Uditha Weerasinghe (Mississippi State University)

GHP_2025_UW_Talk.pdf

16 Dihadron correlation studies in electroproduction from nuclear targets

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 Lab seek to answer both of these questions. We find that the measured correlation functions peak at $\Delta\phi=\pi$ and that this peak is wider for heavier nuclei than for deuterium. We will also give predictions for similar planned measurements in a follow-up experiment with the upgraded CLAS12 detector setup, which features a higher beam energy, higher luminosity, beam polarization (which was absent in the previous measurement), and improvements in particle identification.

Speaker: Ryan Milton (University of California, Riverside)

GHP Meeting 2025 Ryan Milton.pdf

17 --

Parallel Session - Room 252C: Exotic Hadron (Chair: Dhanush Hangel)

Convener: Dhanush Hangal (Lawrence Livermore National Laboratory)

18 Pentaquark Search through J/psi Measurements at Jefferson Lab

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 pentaquark search that waned for a moment after the previous claims at the turn of the millennium turned out to be spurious. Four years after the initial discovery announcement, the LHCb collaboration released new results confirming their previous observation while resolving the previously observed pentaquark state into a double-peak structure and discovering another resonant structure at a lower invariant mass. Today, the true nature of the LHCb’s hidden charm pentaquarks is still unknown and the observation hasn’t been verified in an independent experiment. My talk will focus on the Jefferson Lab experiments that measured the J/ψ photo-production cross section near threshold region to search for these LHCb hidden-charm pentaquark states.

Speaker: Burcu Duran (New Mexico State University)

GHP2025-Duran.pdf

19 How the Contact can Produce Loosely Bound Hadronic Molecules in Heavy-ion Collisions

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 binding momentum of the molecule called the "contact". The production rate of a loosely bound molecule is proportional to the contact density at the kinetic freezeout of the hadron gas. The multiplicity of the molecule is determined by the temperature at kinetic freezeout and the multiplicities of its hadron constituents, and it depends very weakly on the binding energy of the molecule.

Speaker: Justin Pickett (The Ohio State University)

APS Presentation - Justin Pickett.pdf

20 ExoHad Overview: Search for Exotic Hadrons

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 phenomenological models. I will present an overview our program and highlight studies to further our understanding of the excited hadron spectrum.

Speaker: Andrew Jackura (William & Mary)

2025_ghp_Jackura.pdf

21 --

Parallel Session - Room 255B: Nucleon Structure and Spin Physics (Chair: Daniel Pitonyak)

Convener: Daniel Pitonyak (Lebanon Valley College)

22 Nucleon structure in the extreme valence region

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 ratio F2n/F2p of neutron to proton unpolarized structure functions, and provide a first glimpse of the data on spin structure functions accumulated through the RG-C experiment with CLAS12.

Speaker: Dr Sebastian Kuhn (Old Dominion University)

SEKTalk25_forpdf.pdf

23 Small-$x$ Helicity Global Analysis: Now With Polarized $pp$ Data

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 production, $A_{LL}^{\mathrm{jet}}$, at $x_{T,P}\approx \tfrac{p_T}{\sqrt{s}}e^{\pm y} < 0.1$. This analysis serves as a proof-of-principle to determine the effect $pp$ data has on our predictions for helicity PDFs (hPDFs) and the $g_1$ structure function at small-$x$; we utilize the pure-glue $gg \to g$ partonic channel for particle production in polarized $pp$ collisions in place of the jet production cross-section. We modify the large-$N_c\&N_f$ KPS-CTT evolution equations by setting $N_f = 0$ in order to replicate the large-$N_c$ (pure-glue) limit while retaining external quark flavors for the spinor field operators. We find that fitting to even a small number of $pp$ data points makes our spin-contributions, specifically the gluon hPDF $\Delta G$, significantly more positive. Additionally, the inclusion of gluon-sensitive observables reduces our small-$x$ uncertainties for the $g_1$ structure function and hPDFs.

Speaker: Nicholas Baldonado (New Mexico State University)

APS_GHP_presentation.pdf

24 Exploring the Transition Region of QCD with the Proton's g2 Spin Structure Function

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 spin structure functions, which describe hadron spin structure and the moments of which can be directly compared to theoretical predictions. In this talk, I will discuss an experiment which has been recently conditionally approved for running in Jefferson Lab's Hall C, which will measure the g2 spin structure function of the proton in this transition region for the first time, filling in the last significant gap in world data coverage for this quantity for either nucleon, and enabling novel tests of Lattice QCD and other theories which can bridge the low and high $Q^2$ worlds.

Speaker: David Ruth (University of New Hampshire)

DRuth_APSTalk_g2p2.pdf

DRuth_APSTalk_g2p2.pptx

25 Preliminary Results of the SBS-GMn Experiment with Super BigBite Spectrometer at Jefferson Lab’s Hall A

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 experiments in Jefferson Lab's experimental Hall A to extend the high-precision measurements of the remaining nucleon EMFFs up to or beyond Q$^2=10$ (GeV/c)$^2$. The first of these experiments, SBS-GMn (E12-09-019), was completed during the October 2021 to February 2022 run period, aiming to extend the high-precision measurements of the neutron magnetic form factor ($G_M^n$) in the Q$^2$ range of 4 to 13.6 (GeV/c)$^2$ using the ``ratio" method. In this approach, systematic errors are greatly reduced by extracting $G_M^n$ from the ratio of neutron-coincident ($D(e,e'n)$) to proton-coincident ($D(e,e'p)$) quasi-elastic electron scattering from deuteron. In this talk, I will provide an overview of the SBS-GMn experiment, focusing on the physics analysis methodology, and conclude by presenting preliminary results.

Speaker: Dr Provakar Datta (Berkeley Lab)

PDATTA_GHP_2025.pdf

3:40 PM Coffee Break

Parallel Session - Room 252A: Hadrons II (Chair: Sean Dobbs)

Convener: Sean Dobbs (Florida State University)

26 Three-body amplitudes for the analysis of lattice data and experiment

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 talk, construction principles, examples, and applications for three-body amplitudes will be presented, including the axial $a_1(1260)$ and its three-pion dynamics, its determination from lattice QCD, and recent extensions to strangeness channels and complex energies, as well as connections to triangle singularities.

Speaker: Michael Doring (George Washington U and Jefferson Lab)

GHP-2025.pdf

27 Electroproduction of Cascade Hyperons using CLAS12 at Jefferson Lab

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 beam energies of $6.5$ and $7.5$ GeV. These measurements span both the quasi-real photoproduction regime ($Q^2 \leq 0.5$ GeV$^2$) and the purely electroproduction regime ($Q^2 > 0.5$ GeV$^2$), while also shedding light on the still-unclear production mechanisms of cascade. The data for this study were collected using Jefferson Lab's CEBAF Large Acceptance Spectrometer at $12$ GeV (CLAS12). Preliminary results from the exclusive electroproduction reaction $ep \rightarrow e'K^+K^+(\Xi^-)$ will be presented.

Speaker: Bianca Gualtieri (Florida International University)

BGualtieri_GHP_final.pdf

28 Refined Simulations of Double Pion Electroproduction for CLAS22

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 in terms of detector coverage and reconstructed simulation. Sufficient resolution is necessary for precise identification and isolation of exclusive and missing particle (proton, π+, and π−) topologies. These simulations aid in current data analyses and provide a foundation for future experiments with CLAS22 at Jefferson Lab, ultimately leading to a deeper understanding of the baryon structure.

Speaker: Alexis Osmond (University of South Carolina)

GHP_AOsmond.pdf

29 The CEBAF Experimental Program and Possible Future Upgrades

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 upgrades such as a positron source (12GeV) and higher electron beam energies (22GeV).

Speaker: Dr Douglas Higinbotham (Jefferson Lab)

GHP-Higinbotham.pdf

GHP-Higinbotham.pptx

Parallel Session - Room 252B: Electroproduction from nuclear targets II (Chair: Sebastian Kuhn)

Convener: Sebastian Kuhn (Old Dominion University)

30 Meson Photoproduction as a Measure of SRC Universality

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 well as assumptions of factorization between the reaction and the nuclear ground state. In Fall 2021, our collaboration conducted an experiment in Hall D at Jefferson Lab using a real photon beam on nuclear targets to independently probe the properties of SRCs. Here we present the measurement of SRC breakup events using quasi-elastic ρ- meson photoproduction from correlated neutrons in deuterium, helium, and carbon nuclei and compare with phenomenological predictions using ab-initio nuclear calculations. We use this common theoretical framework to demonstrate consistency across electron-, proton-, and photon-scattering measurements, providing strong evidence for the universality of SRC ground-state properties across different hard reactions.

Speaker: Jackson Pybus (LANL)

SRC Universality.pdf

31 Searching for 3-nucleon short-range correlations

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 extremely high nucleon momenta. However, experimental efforts so far have not provided definitive evidence for their existence.

In this talk, I will review possible 3N SRC configurations, experimental methods, and the results from past 3N SRC searches. I will also discuss future plans to search for 3N SRC signals at Jefferson Lab.

Speaker: Shujie Li (Lawrence Berkeley Lab)

2025_GHP_3N_SRC_ShujieLi.pdf

32 In-medium nucleon Structure Functions through tagged Deep Inelastic Scattering with the LAD experiment

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 nucleons within Short Range Correlated (SRC) pairs, while mean-field nucleons remain largely unaltered.
The LAD experiment, conducted in Hall C of Jefferson Lab, aims to test this hypothesis using spectator-tagged DIS. The experimental setup includes a large acceptance detector (LAD) comprised of GEMs, and scintillator bars, which complements Hall C’s existing high resolution spectrometers. By tagging backward spectator protons, LAD will provide detailed insights into the initial state of the deuteron and its associated quark structure.
This presentation will outline the current status of the LAD experiment and discuss its connection to other ongoing experimental and theoretical advancements.

Speaker: Carlos Ayerbe Gayoso (Old Dominion University)

C.Ayerbe-GHP-20250317_final.pdf

33 --

Parallel Session - Room 252C: Heavy Ion Collisions and Saturation (Chair: Rosi Reed)

Convener: Rosi Reed (Lehigh U)

34 Can a universal nPDF picture describe di-hadron saturation signals?

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 of the initial state of the cold nucleus, such as from coherent multiple scattering or within a glasma calculation framework. A key topic in heavy-ion and future EIC physics is the search for the onset of gluon saturation effects, which should give rise to a variety of effects besides just the simple (x,Q^2)-dependent shadowing encoded in the nPDFs. For example, measurements of forward di-hadron or di-jet correlations are widely accepted in the community to be sensitive to the onset of non-linear QCD dynamics. However, I argue that a straightforward application of the nPDF modifications in modern nPDF sets to recent measurements by ATLAS at the LHC and STAR at RHIC can partially or fully describe the signals observed in these data in a quantitative way, purely via a (x,Q^2)-dependent reweighting of cross-sections and without including any additional dynamics. This example highlights an important question in the GHP community as to what extent these paradigms are overlapping and what range of phenomena each should be expected to describe.

Speaker: Dennis Perepelitsa (University of Colorado Boulder)

dvp-GHP-3-14-25.pdf

35 Baryon number dynamics from RHIC to the LHC

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.

Speaker: David Frenklakh (Brookhaven National Laboratory)

DF_baryon_dynamics_talk_1.pdf

36 Recent CMS heavy flavor spectroscopy

The CMS experiment has conducted extensive research in heavy flavor spectroscopy, revealing significant findings in both exotic hadron production and traditional hadron decays. Recent results include the first evidence for the production of the exotic state (X(3872)) in heavy-ion collisions, providing new insights into its internal structure and production mechanisms. Additionally, new structures have been observed in the (J/\psi J/\psi) mass spectrum, including a previously unreported resonance in (J/\psi J/\psi \to \mu^+\mu^- \mu^+\mu^-). These studies contribute to understanding the nature of exotic multiquark states. Beyond exotic hadrons, CMS has also observed new decay channels in conventional baryons and mesons. This includes the first observation of ( B^0 \to \psi(2S) K_S^0 \pi^+ \pi^- ), ( \Lambda_b^0 \to J/\psi \Xi^- K^+ ), and ( \Xi_b^- \to \psi(2S) \Xi^- ), expanding our knowledge of hadron decays involving heavy quarks. These results provide crucial experimental input for testing quantum chromodynamics models and improving our understanding of hadronic structure.

Speaker: Xining Wang (Tsinghua University)

GHP2025.pdf

37 Entanglement and thermalization in jet production in the massive Schwinger model

The possible link between entanglement and thermalization, and the dynamics of hadronization are addressed by studying the real-time response of the massive Schwinger model coupled to external sources. This setup mimics the production and fragmentation of quark jets, as the Schwinger model and QCD share the properties of confinement and chiral symmetry breaking. By using quantum simulations on classical hardware, we study the entanglement between the produced jets, and observe the growth of the corresponding entanglement entropy in time. This growth arises from the increased number of contributing eigenstates of the reduced density matrix with sufficiently large and close eigenvalues. We also investigate the physical nature of these eigenstates, and find that at early times they correspond to fermionic Fock states. We then observe the transition from these fermionic Fock states to meson-like bound states as a function of time. In other words, we observe how hadronization develops in real time. At late times, the local observables at mid-rapidity (such as the fermion density and the electric field) approach approximately constant values. We find that the same observables can be extracted from a thermal massive Schwinger model with one universal value of the temperature, thus establishing the onset of thermalization in this system.

Speaker: David Frenklakh (Brookhaven National Laboratory)

DF_Entanglement_and_thermalization_talk_2.pdf

Parallel Session - Room 255B: Compton Scattering (Chair: Richard Tyson)

Convener: Richard Tyson (Jefferson Lab)

38 DVCS at CLAS12 on Longitudinally Polarized Protons and Neutrons in Deuterium

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 Group C (RGC) experimental program with the CLAS12 detector at Jefferson Lab aims to measure, for the first time, the DVCS target-spin and double-spin asymmetries on protons and neutrons in deuterium. RGC relies on longitudinally polarized hydrogenated- and deuterated-ammonia targets. An overview of the experiment and of the analysis for DVCS on protons and neutrons in deuterium will be presented, highlighting the challenges of working with a polarized nuclear target, the techniques that have been developed to address them, and preliminary results for the asymmetries.

Speaker: Noémie Pilleux (Argonne National Laboratory)

GHP_March2025_Pilleux.pdf

39 Timelike Compton Scattering perspectives at Jefferson Lab

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 for the GPDs, as well as complement data bases for Compton Form Factors extractions. Therefore, we are developing new dedicated experiments for JLab Hall C. In this talk, we will discuss two experiments we are developing, namely unpolarized and transversely polarized TCS with a dedicated setup for Hall C. We will also discuss the complementary measurements that can be made with GlueX (Hall D) to bring new independent constraints on the real part of the Compton amplitude.

Speaker: Debaditya Biswas (Virginia Tech)

biswas_GHP_2025.pdf

40 Measuring TCS and DDVCS at JLab Hall C

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 of the nucleon's content, however, this is assuming we can decorrelate it's kinematic variable dependencies to relate it to actual measurements. This is possible if we can measure DDVCS. Therefore, we are developing a dedicated experiment for this reaction. Since it involves the development of a new muon detector, we will discuss this project as well as the other experimental challenges.

Speaker: Marie BOER (Virginia Tech)

GHPMarch2025_marieboer.pdf

41 Development of a new muon detector for JLab Hall C

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 from pions at relatively low momentum. We would like to present our progress and the status of this R&D work, and discuss the perspectives for other experiments beyond JLab.

Speaker: Mahmoud Gomina (Virginia Tech)

Mahmoud_GHP_Final.pdf

Saturday, March 15

Plenary Session - Room 255B: III (Chair: Daniel Pitonyak)

Convener: Daniel Pitonyak (Lebanon Valley College)

42 UPCs at RHIC and the LHC

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 photon fields that facilitate photon-photon and photon-nucleus interactions at unprecedented energy scales. In this talk, I will present recent experimental and theoretical progress in the study of UPCs, focusing on the vector meson productions in nuclei via coherent and incoherent photoproduction processes. I will also discuss how UPCs provide constraints on nuclear shadowing and saturation effects, including potential measurements to distinguish between these phenomena. Lastly, I will highlight future prospects for UPC research and its implications for advancing our understanding of the fundamental structure and dynamics of matter.

Speaker: Zhoudunming Tu (BNL)

GHP2025-Tu.pdf

43 Charming Experiment Finds Gluon Mass in the Proton

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 highlight key results from the J/ψ-007 experiment in Hall C, which performed the first measurement of the differential cross-section for J/ψ photoproduction near threshold. This analysis enabled the determination of the proton’s gluonic gravitational form factors (GFFs) directly from experimental data. The J/ψ-007 results revealed that the proton's mass radius is smaller than its charge radius, with evidence for a scalar gluon cloud extending beyond the charge radius to about 1 femtometer.

The focus of this talk will be on new results from the J/ψ → μ⁺μ⁻ decay channel, which effectively doubles the 2023 dataset and significantly improves constraints on the gluonic GFFs. This expanded dataset allows for the extraction of pressure and shear distributions of gluons within the proton, offering deeper insights into its internal mass and mechanical structure. I will also preview the forthcoming experimental program with SoLID at Jefferson Lab and ePIC at the Electron-Ion Collider.

Speaker: Sylvester Joosten (Argonne National Laboratory)

Joosten-GHP2025-Jpsi.pdf

44 Experimental outlook for Color Transparency phenomena

Searching for evidence of Color Transparency (CT) is a vibrant experimental effort to observe hadrons in a small color-neutral transverse size configuration in the nucleus. CT is fundamentally predicted by quantum chromodynamics and is expected to be observable in exclusive scattering as a reduction of final state interactions (FSI) of the point-like hadron with the nuclear medium. The observation of the onset of CT lies at the intersections between the quark-gluon degrees of freedom and the nucleonic descriptions of nuclei. Experimentally, this would be observable as a rise in the measured transparency of the point-like hadron with increasing four-momentum transferred.

Searches for CT effects in mesons and baryons in electroproduction experiments at Jefferson Lab have yielded somewhat differing conclusions. Observations of CT in rho and pi+ electroproduction in the 6 GeV beam era at Jefferson Lab already established indications of an early onset of CT, and new experiments are extending these measurements to higher momenta in Halls B and C. However, the most recent experimental effort for the onset of CT in protons in Hall C ruled out observations up to a Q2=14 GeV2 in contrast with theory expectations. A future experiment will explore the onset of CT in protons in rescattering kinematics with an enhanced sensitivity to protons in point-like configurations. Furthermore, a photoproduction experiment in Hall D at Jefferson Lab explores CT phenomena through other reaction mechanisms. This talk will present the current experimental statuses of the recent experiments and opportunities in new future measurements.

This work was funded in part by the U.S. Department of Energy, including contract AC05-06OR23177 under which Jefferson Science Associates, LLC operates Thomas Jefferson National Accelerator Facility.

Speaker: Holly Szumila-Vance (FIU)

GHP_CT_2025.pdf

45 Understanding Hadron Structure by combining Lattice QCD and Phenomenology

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 fraction x. This complementarity could be beneficial in extractions of PDFs, TMDs, and GPDs. In this talk I will highlight a few specific cases where modern lattice QCD could have significant impact.

Speaker: Joe Karpie (Jefferson Lab)

Karpie_ghp_2025.pdf

10:30 AM Coffee Break

Plenary Session - Room 255B: IV (Chair: Megan Connors)

Convener: Megan Connors (Georgia State University)

46 Results from the Relativistic Heavy Ion Collider Beam Energy Scan II

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.

Speaker: Shusu Shi (Central China Normal University)

Results from the Relativistic Heavy Ion Collider Beam Energy Scan II .pdf

47 Probing the quark gluon plasma with jets

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 sprays of particles originating from highly energetic quarks and gluons, play a crucial role in these investigations. Due to their dynamic nature and the complex evolution into hadrons, interactions between jets and the QGP offer valuable insights into the inner workings of the QGP. In this talk, I will discuss some of the exciting developments in the study of QGP using jets as a probe.

Speaker: Yi Chen (Vanderbilt University)

20250315_JetInHeavyIon_GHP2025_YiChen_v14.pdf

48 Energy-Energy Correlators and Connections to Transverse Momentum Structure

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 extracting the Collins-Soper kernel, a critical quantity governing the rate of TMD evolution.

Speaker: Zhongbo Kang (UCLA)

Energy-Energy Correlators and Connections to Transverse Momentum Structure

12:30 PM Lunch Break

Parallel Session - Room 252A: Hadrons III (Chair: Alessandra Filippi)

Convener: Alessandra Filippi (INFN Torino)

49 Search for Axion-Like-Particles in $\eta$ meson decays with the HADES Detector

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 the HADES physics program is to test the predictions of the Standard Model and search for potential hints of new phenomena beyond current theoretical frameworks (BSM – Beyond Standard Model Physics). In particular, by studying $\eta$ meson decays into dilepton ($e^{+}e^{-}$) channels, we investigate the possible existence of the $X_{17}$ boson, a candidate for an Axion-Like Particle (ALP) [2]. In this scenario, an intermediate state of the $\eta$ meson decay could involve the creation of a new particle through the sequence $\eta\to\pi^{+}\pi^{-} X_{17} (\to e^{+}e^{-}$). The $X_{17}$ particle is hypothesized to be iso-scalar or axial-vector gauge boson, which may mediate a fifth force with couplings to Standard Model particles [3].
These studies are further motivated by recently observed anomalies in the invariant mass distribution of $e^{+}e^{-}$ pairs in isoscalar magnetic nuclear transitions of $^{8}Be$ and $^{4}He$ nuclei [3-5]. These anomalies have been interpreted as evidence for the creation and decay of an intermediate particle, $X_{17}$, with a mass of approximately 17 MeV/$c^{2}$ and suppressed mixing with the neutral pion.
In this talk, we will discuss the general motivations for ALP studies, present our analysis methodology, and share preliminary results from data collected using the high-resolution HADES spectrometer.

Bibliography:
[1] G. Agakichiev et al. (HADES), Eur. Phys. J. A 41, 243 (2009).
[2] D. S. M. Alves, Phys. Rev. D 103, 055018 (2021)
[3] J. L. Feng et al., Phys. Rev. Lett. 117, 071803 (2016).
[4] A. J. Krasznahorkay et al., Phys. Rev. Lett. 116, 042501 (2016).
[5] A. J. Krasznahorkay et al., Phys. Rev. C 104, 044003 (2021).

Speaker: Marcin Zielinski (Jagiellonian University in Krakow)

HADES-X17-APS-Anaheim-15.03.2025-MarcinZielinski.pdf

50 Resolving the X17 Anomaly with the PRad Spectrometer at Jefferson Lab

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 force. We will run an experiment in Hall B of Jefferson Lab that will search for this proposed particle using Bremsstrahlung-like production in the photon field of a thin tantalum target. Our experiment aims to fully resolve the anomaly by having sensitivity to the full coupling constant spectrum that has not already been ruled out by other experiments. We are scheduled to run our experiment at the start of the FY2026 CeBAF run period. In this talk I will discuss the motivation for this experiment, as well as design decisions, preparations, and planning for the upcoming run.

Speaker: Tyler Hague (JLab)

X17Experiment.pdf

51 Symmetry of vacuum observed in meson-nucleus bound systems

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. Also, there are experiments to search for eta'-mesic nuclei, which may serve information on the axial U(1) anomaly. We will discuss the achievements and the present status of these experimental challenges together with the future perspectives.

Speaker: Kenta Itahashi (RIKEN)

2025itahashi-GHP-open.pdf

52 Topics of Spin

Speaker: Dennis Sivers (Portland Physics Insitute)

DennisSivers-anapres.pptx

Parallel Session - Room 252B: Lattice calculations of parton distributions (Chair: Michael Doring)

Convener: Michael Doring (George Washington U and Jefferson Lab)

53 Proton GPDs from Lattice QCD

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 extract GPDs. On the twist-2 level, there are four transversity GPDs: $H_T$, $E_T$, $\tilde{H}_T$, and $\tilde{E}_T$. Traditionally, calculations have been conducted in the symmetric frame but was computationally expensive. As shown in Phys.Rev.D 106 (2022) 11, 114512, an optimized calculation of GPDs has been done allowing to gain more values of -t at a reduced computational cost. Calculations presented here use an ensemble where $N_f=2+1+1$ with twisted mass fermions and a clover improvement. The light-quark masses lead to a simulated pion mass of 260 MeV. All calculations done are at zero-skewness.

Speaker: Joshua Miller (Temple University)

GHP_2025_Miller_Final.pdf

54 Recent Progress in Gluon Parton Distributions from Lattice QCD

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 chiral symmetry breaking which gives rise to hadron mass. Obtaining good signal for the gluon PDFs can be challenging for both phenomenological and lattice studies due to limited experimental data and poor signal at long distances respectively. We discuss calculations of the proton and pion PDFs from the pseudo-PDF methodology at various lattice spacings and pion masses, with a continuum-physical extrapolation of the proton PDF. We present the results of a joint study with the JAM collaboration using lattice gluon data to constrain a global fit of the pion PDFs. We conclude with comments about current and future application of large momentum effective theory to the gluon PDF and new signal improvement techniques, which are expected to push towards a new generation of gluon distribution calculations from lattice QCD.

Speaker: William Good (Michigan State University)

GHP_Slides_v1.pdf

55 Toward Extracting the Scattering Phase Shift from Integrated Correlation Functions in LQCD

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 increased, which offers a suitable framework to overcome the challenges that the Luscher formula faces at large volume limit.

Speaker: Peng Guo (Dakota State University)

Peng_Guo_GHP2025_March.2025.pdf

56 On inflation scenarios and dark energy in a scaled gravity

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 tensor-to-scalar ratio r via the slow-roll analysis, we provide certain inflationary constraints on β from the Planck observational and the recent released BICEP/Keck data. By means of a possible Higgs-inflaton coupling, we discuss dark energy in the proposed scaled gravity within such an inflation model.

Speaker: Mr Mustapha LAMAAOUNE (Mohamed V university)

GHP presentation.pdf

Parallel Session - Room 252C: Jet Production (Chair: Megan Connors)

Convener: Megan Connors (Georgia State University)

57 Energy-energy correlators in jets across collision systems

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 flow within jets. In pp collisions, the angular dependence of the EEC cross section shows a distinct separation of the perturbative and non-perturbative regimes, revealing the partonic dynamics of jet formation and the confinement of partons into hadrons. In heavy flavor jets, the EEC offers valuable insight into flavor dynamics of QCD parton fragmentation and hadronization, such as the different Casimir factors of quarks and gluons, as well as the mass of heavy quarks. Measurements of the EECs for inclusive jets in p-Pb and Pb-Pb probe the modifications to jet evolution caused by interactions with a cold nuclear medium and the quark-gluon plasma, respectively. In this talk, we present ongoing EEC measurements and the broad insights they offer into jet structure and jet-medium interactions.

Speaker: Anjali Nambrath (UC Berkeley)

GHP25 EECs.pdf

58 First evidence of the medium response to hard probes with Z-hadron correlations in PbPb and pp collisions at \sqrt{s_{NN}} = 5.02 TeV

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 $1.67 \pm 0.03$ nb$^{-1}$, complemented by proton-proton (pp) data from 2017 with $301 \pm 6$ pb$^{-1}$. Events are selected with at least one $Z$ boson having $40 < p_\mathrm{T} < 350$ GeV, and charged-hadron distributions are examined in $p_\mathrm{T}$ bins to investigate potential in-medium parton-shower modifications and medium-recoil effects.

A significant modification is observed in the azimuthal and pseudorapidity distributions of charged hadrons with $p_\mathrm{T}$ in the range of 1–2 GeV in $\mathrm{PbPb}$ collisions compared to pp references. These results align with phenomenological models, such as the Co-LBT Hydro and HYBRID models, that incorporate the positive and negative wake effects associated with the fast moving-quarks and gluons in the Quark-Gluon Plasma (QGP).

This analysis provides crucial new insights into the interplay between hard and soft particle production in heavy-ion collisions. By comparing PbPb data with pp baselines and theoretical predictions, the findings offer the first experimental evidence for medium-recoil and medium-hole effects induced by a hard probe, contributing to a deeper understanding of jet quenching mechanisms in the QGP.

Speaker: Prof. Yen-Jie Lee (Massachusetts Institute of Technology)

20250315-yenjie-GHP-NA-v6.pdf

20250315-yenjie-GHP-v6.pptx

59 Subeikonal corrections to dijet production in DIS

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 contribution of the transverse components of the field as well, but also from the $x^+$ dependence of the Wilson line. We also outline the calculation to extract higher order subeikonal corrections.

Speaker: Tiyasa Kar (NCSU)

Tiyasa_GHP2025.pdf

60 Exploring QCD with light and heavy flavor jet substructure measurements

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 QCD radiation around massive quarks, i.e., dead-cone effect. Furthermore, measuring jet substructure observables in heavy-ion collisions have provided unique channels to study the mechanisms of jet interactions with the hot and dense QCD medium created in these collisions, referred to as Quark-Gluon Plasma (QGP). The jet-QGP interactions in heavy-ion collisions is expected to depend on the mass of the initiating parton and can be studied by comparing light- and heavy-flavor jet measurements. In this talk, I will present jet substructure results that have shaped our understanding of jet evolution in vacuum and their interactions with the QGP. I will also present on potential light- and heavy-flavor jet measurements that can provide strong constraints on jet-QGP interactions.

Speaker: Dhanush Hangal (Lawrence Livermore National Laboratory)

APS_GHP_2025_Hangal.pdf

APS_GHP_2025_Hangal.pdf

Parallel Session - Room 255B: Artificial Intelligence, Machine Learning, Computing I (Chair: Patrick Barry)

Convener: Patrick Barry (Argonne National Lab)

61 AI generative models for hadron physics analyses

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. Solving this challenge requires nuclear physics to develop and adopt methods from data science, AI/ML, applied mathematics, and large-scale computing and adapt them to this goal. The A(i)DAPT working group is deploying machine learning physics event generators (MLEGs) based on AI generative models to faithfully mimic distributions of final state particle momenta, unfold the detector-induced distortions, and gain new insight into non perturbative QCD. In this contribution, results obtained by the A(i)DAPT WG will be reported.

Speaker: Marco Battaglieri (JLab/INFNGE)

A(i)DAPT_GHP25.pdf

62 GPU-based Online Reconstruction for SpinQuest Studies at Fermilab

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 off a transversely polarized parton, carrying a momentum fraction $(x)$, within a transversely polarized nucleon with its spin aligned or anti-aligned to its parent spin. Such a study provides critical insights into sea quarks' contributions to nucleon polarization. To this end, a multi-threaded Graphics Processing Unit (GPU) algorithm has been developed to perform real-time data processing and monitoring with optimized parallelization capabilities. In this talk, the performance of the GPU-based online reconstruction and visualization algorithm will be presented, followed by a description of ongoing efforts to accomplish a model-independent extraction of $h_1(x)$ distributions.

This work is supported in part by the U.S. DOE award $\#$: DE-FG02-07ER41528.

Speaker: Utsav Shrestha (Mississippi State University)

APSGHP_Utsav.pdf

63 Overview of ALERT AI-assisted Track Reconstruction and Particle Identification Project

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 and 4He, and thus, study the related in-medium stimulated effects and their impact on the correlated three-dimensional Generalized Parton Distributions. The planned 2025 CLAS12 experiment aims to use the newly built a low energy recoil tracker (ALERT) detector to study tagged DVCS on 4He with an 11 GeV beam energy via the detection of low-momentum recoil fragments such as 2H, 3H, 3He, 4He, and protons, down to 70 MeV/c, in a wide kinematical range. The ALERT detector enables effectual separation between various recoil ions by integrating a hyperbolic drift chamber (AHDC) with a time-of-flight (ATOF) array.

Recent advances in artificial intelligence (AI), such as new model architectures, have proven effective for high-rate experiments with substantially elevated background noise, such as AHDC in ALERT. AI is deployed in ALERT experiments to enhance AHDC track-finding efficiency, purity, and speed compared to conventional algorithms as well as particle identification in conjunction with ATOF. In this talk, an overview of the ALERT physics program will be provided alongside the ongoing development and optimization of the AI-assisted track reconstruction and particle identification techniques.

This work is supported in part by the U.S. DOE award #: DE-FG02-07ER41528.

Speaker: Mathieu Ouillon (Miss State U.)

GHP_031525.pdf

64 AI/ML in Streaming Data Processing at the EIC

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 holistic approach enables event selection by utilizing all available detector data, eliminating trigger bias, and providing accurate uncertainty estimation. Moreover, prompt background measurements through streaming readout play a critical role in reducing background noise and associated systematic uncertainties, pushing the boundaries of experimental precision.

AI plays a significant role in optimizing the data processing pipeline. Autonomous alignment, calibration, and validation help accelerate data turnaround. Beyond this, AI has the potential to enhance detector systems at ePIC through autonomous experimentation and control. For instance, a smart detector system could dynamically adjust thresholds based on background rates, ensuring optimal performance in near real time.

This talk will highlight streaming readout and AI applications at ePIC, showcasing their potential to redefine experimental capabilities and precision.

Speaker: Markus Diefenthaler (Jefferson Lab)

Diefenthaler-GHP2025-AIStreamingEIC.pdf

3:40 PM Coffee Break

Parallel Session - Room 252A: Hadrons IV (Chair: Marcin Zielinski)

Convener: Marcin Zielinski (Jagiellonian University in Krakow)

65 Light meson spectroscopy: experimental status

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 for decades many experimental efforts.
Meson spectroscopy provides a valuable framework for studying quark interactions and the role of gluons. This includes identifying conventional mesons and searching for unconventional states such as multiquark aggregates, hybrids, and glueballs. States with exotic quantum numbers present unique opportunities for discovery, yet many observed candidates exhibit ordinary quantum numbers. This complicates their interpretation due to large widths and shared decay patterns within overlapping mass ranges.
This talk will review recent experimental progress in light meson spectroscopy, studying hadrons composed by the lightest (u, d, s) quarks only in the mass range below 2 GeV/c². It will highlight results from various processes, including e+e- and Nucleon-Antinucleon annihilation, hadron scattering, and electro- and photoproduction. Especially in the latest years advances in analysis techniques and lattice QCD have been instrumental, offering new tools to disentangle these complex phenomena for a deeper understanding of the strong interaction and QCD’s non-perturbative regime: A short description of some expectations from theory will be discussed, related to the most recent experimental observations.

Speaker: Alessandra Filippi (INFN Torino)

ghp2025_filippi.pdf

66 JLab Eta Factory

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 confinement. In addition, the η/η′ meson has quantum numbers of vacuum (except parity) with its strong and electromagnetic decays being either anomalous or forbidden to the lowest order due to symmetries or angular momentum conservation. This enhances the relative importance of higher order contributions, making rare η/η′ decays a sensitive hadronic probe for weakly-coupled new forces. Searching for sub-GeV dark gauge boson candidates and the C-violating, P-conserving interactions in various η/η′ decays will extend our knowledge of the dark sector and explore new sources of CP violation that are needed to explain the observed matter and anti-matter asymmetry in the universe. The JLab Eta Factory experiment is aimed at simultaneous measurements of η and η′ decays, with emphasis on rare neutral mode. This experiment will start in spring 2025 using the GlueX apparatus with a newly upgraded Forward calorimeter. The status and the new experimental opportunities for the η/η′ physics will be presented.

Speaker: Prof. Liping Gan (University of North Carolina Wilmington)

JEF-GHP25-Gan-pdf.pdf

67 Pion vector form factor across spacelike and timelike regions from lattice QCD

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 generalization of the Lellouch-Lüscher formalism for coupled channels, which in this case corresponds to the pion and kaon vector-isovector timelike form factors.
We show that the spacelike and elastic timelike regions can be described simultaneously with parameterizations satisfying analyticity and unitarity.
Subsequently, we show that our coupled-channel determination is consistent with the determination restricted to the elastic region.
This work demonstrates the capability of LQCD calculations to go beyond the determination of form factors restricted to only spacelike or only elastic timelike regions.

Speaker: Felipe Ortega-Gama (UC Berkeley)

TL_pion_ff_GHP.pdf

68 Recent and future experiments exploring Nucleon-to-Delta transition form factors at Jefferson Lab

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 talk we will discuss collected and proposed measurements of the TFFs in Hall C at JLab, utilizing the SHMS and the HMS spectrometers, that focus on low four-momentum transfer squared where the mesonic cloud dynamics are dominant and rapidly changing. Possible future experiments pursuing bound neutron excitation with the CLAS12 and ALERT detectors, as well as large Q$^2$ measurements with the SoLID detector and beam energy upgrades at JLab, will also be discussed.

Speaker: Michael Paolone (New Mexico State University)

TFFs_GHP_25.pdf

Parallel Session - Room 252B: Ultra-Peripheral Collisions (Chair: Dennis Perepelitsa)

Convener: Dennis Perepelitsa (University of Colorado Boulder)

69 Recent results on vector meson photoproduction and interference effects in Ultra Peripheral Collisions at STAR

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 have been made to study this interference effect in RHIC and LHC experiments. Recently, STAR at RHIC observed spin interference effect from the $\rho^{0}$ vector meson photoproduction in Au+Au and U+U UPCs. Nevertheless, determining whether interference happens at the vector meson level or among its decay daughters is not feasible using $\rho^{0}$ data. This is because both the $\rho^{0}$ and its decay pions are bosons, and the $\rho^{0}$ has short lifetime. On the other hand, the $J/\psi$ vector mesons decay into two fermions, having a longer lifetime and a non-localized wave function, which brings more information on the aforementioned phenomenon.

In this talk, we will report measurements of the differential cross sections of photoproduced $J/\psi$ in Au+Au, Ru+Ru and Zr+Zr UPCs at $\sqrt{s_{_\mathrm{NN}}}=200$ GeV recorded by STAR. The results will be presented for different combinations of neutron emissions. %, which can be used to resolve the photon energy ambiguity.
These data provide important constraints for nuclear parton distribution functions and sub-nucleonic shape fluctuations in heavy nuclei.
We also present the latest measurements of the angular modulation arising from the spin interference effect for coherent $J/\psi$ photoproduction in Au+Au, Ru+Ru and Zr+Zr UPCs. The physical implications of these measurements will be discussed together with model comparisons. Finally, we will discuss future prospects of these measurements during the final 2025 RHIC run.

Speaker: Ashik Ikbal Sheikh (Kent State University)

star_upc_aps_ghp_march2025_ashik.pdf

70 Ultra-peripheral collisions at LHCb

The LHCb experiment is a unique tool for studying ultra-peripheral heavy-ion collisions (UPCs) at the LHC. The LHCb spectrometer's forward acceptance provides sensitivity to extremely low-momentum partons in the nucleus and allows for the reconstruction of low-mass resonances produced in UPCs. Furthermore, LHCb's particle identification capabilities allow for the study of a wide range of final states, providing new opportunities to study pomeron- and photon-induced interactions with heavy nuclei. This talk will discuss recent studies of UPCs with the LHCb detector, from light hadron to heavy quarkonium production.

Speaker: Thomas Boettcher (Los Alamos)

boettcher_APSGHP2025.pdf

71 First energy-dependent measurement of incoherent J/Psi photoproduction in PbPb UPCs at 5.02 TeV with the CMS experiment

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 sensitive to the local gluon density fluctuations at both nucleonic or subnucleonic levels. Thus, the systematic measurement of energy-dependent $\rm{J}/\psi$ photoproduction could
explore the evolution of gluonic structures within nuclei in detail, with potential implications for uncovering the onset of gluon saturation at sufficient small-x regime.

In this talk, we present the first energy-dependent measurement of the incoherent $\rm{J}/\psi$ photoproduction cross section in PbPb UPCs at the LHC with the CMS experiment, using the forward neutron tagging to cover a wide photon-nucleon center-of-mass energy range from 40 to 400 GeV. This allows us to explore fluctuating gluon fields over a broad Bjorken-x range, extending into the uncharted region of x<10^-4. Furthermore, we report the ratio of incoherent to coherent \rm{J}/\psi$ production and evaluate the nuclear suppression factor for the incoherent production as a function of x. By comparing state-of-the-art theoretical predictions, these results offer unique insights into gluon fluctuations and have important implications for understanding nuclear gluon distributions and saturation phenomena.

Speaker: Xiao Huang (Rice University)

incohHX.pdf

72 Constraining nuclear PDFs at low-x with the first measurements of the D0 production in ultraperipheral heavy ion collisions with CMS

In this talk, we present the first measurement of $\mathrm{D}^0$ photoproduction in heavy ion ultraperipheral collisions (UPCs) using the data collected by CMS experiment during 2023 PbPb collisions at LHC. The measured production cross sections are presented as a function of the $\mathrm{D}^0$ transverse momentum (2<p$_T$<12 GeV/c) and rapidity (-2<y<2). The results are compared to theoretical calculations that exploit different modeling of the nuclear parton distribution functions (nPDFs) and provide new constraints into the properties of nuclear matter at low x and for Q$^2$ ranging from O(10) to O(100) GeV$^2$, in absence of significant final-state effects.

Speaker: Gian Michele Innocenti (MIT)

20250315_APSGHP2025_Innocenti.pdf

Parallel Session - Room 252C: Heavy Ion Collisions and Nuclear Structure (Chair: Prithwish Tribedy)

Convener: Prithwish Tribedy (Brookhaven National Lab.)

73 Physics Potential, Accelerator Options, and Experimental Challenges of a TeV-Scale Muon-Ion Collider

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 facilitating precision QCD and electroweak measurements and searches for beyond Standard Model physics. We discuss the potential physics program of a muon-ion collider and summarize some accelerator design options. New studies on unique key physics observables in $\mu$-p and $\mu$-nucleus will be presented. The associated experimental challenges from beam-induced backgrounds on physics signals are also explored. Initial studies of a forward muon spectrometer design applicable for a muon-ion or muon-muon collider experiment will be presented.

Speaker: Wei Li (Rice University)

MuIC_GHP_WeiLi_03152025_v3.pdf

74 Probing Nuclear Structure of Heavy Ions at the Large Hadron Collider

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 geometry.
These flow ratios are also sensitive to nuclear skin thickness, providing indirect constraints on neutron skin. We also explore opportunities at upcoming SMOG2 experiments at LHCb. Using ab initio calculations for $O$ and $Ne$, we predict anisotropic flow for Pb+Ne and Pb+O collisions. Elliptic flow in Pb+Ne is enhanced due to Ne's unique shape.

This research creates new synergies between nuclear structure and heavy-ion physics, advancing precision studies in relativistic nuclear collisions.

Speaker: Wenbin Zhao (Wayne State University)

Wenbin_Zhao_APS.pdf

75 Exploring the role of the pre-equilibrium phase in determining nuclear geometry in high-energy collisions

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, while neglecting the pre-thermal phase. In this presentation, we study the impact of a free-streaming phase on observables and point out some for which it is relevant. The discussion in terms of geometrical estimators follows arXiv:2305.03703v3. Furthermore, we present initial results from full hydrodynamic simulations to assess the geometric estimators that were used

Speaker: Kevin Possendoro Pala (University of Illinois Urbana-Champaign)

ghp.pdf

76 Tagging coherent vector-meson production events at the Electron-Ion Collider

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 resulting from nuclear de-excitations can serve as a means of tagging events where an incoherent electron-ion interaction has occurred. This talk provides estimates of the capability of the ePIC detector to tag incoherent events by utilizing photons emitted during nuclear de-excitation. Additionally, different nuclear target species (Au, Pb) are compared, and implications for their viability in studying exclusive vector-meson production at the EIC and ePIC are discussed.

Speaker: Mathias Labonte (University of California)

IncoherentEvents_With_BeAGLE.pdf

Parallel Session - Room 255B: Artificial Intelligence, Machine Learning, Computing II (Chair: Markus Diefenthaler)

Convener: Markus Diefenthaler (Jefferson Lab)

77 From uncertainty to discovery: machine learning at the frontier of phenomenology

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 phenomenological global fits including beyond the Standard Model (BSM) physics scenarios. By leveraging variational autoencoders (VAEs) and contrastive learning with similarity metrics, I investigate how the inherent uncertainties in fits of collinear PDFs impact the landscape of new physics models. Incorporating novel methods such as evidential deep learning, we define a new information theory metric to understand parametric theory overlaps and redundancies. My work aims to enhance our understanding of nonperturbative QCD through next generation machine learning models, ultimately pushing the frontier of particle physics discovery.

Speaker: Brandon Kriesten (Argonne National Lab)

Kriesten_GHP2025.pdf

78 Quantum Algorithms for high energy evolution

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) JIMWLK admits a formulation as a Langevin equation, allowing for classical simulations, the next-to-leading order (NLO) JIMWLK remains a significant computational challenge.
Recently, it was shown that the JIMWLK equation for hadronic density matrices can be expressed as a Lindblad equation, enabling formulation as a quantum simulation of an open quantum system. This work maps the functional problem to a simplified toy quantum system in zero dimensions. It proposes a quantum algorithm to solve the Lindblad-JIMWLK equation in this reduced setting.

Speaker: Shaswat Tiwari (North Carolina State University)

Talk_Lindblad_JIMWLK_Shaswat_S_Tiwari.pdf

79 An overview of the MUSES cyberinfrastructure and what it can do for you

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 first-principle theories and models across the multidimensional QCD phase diagram, including thermodynamics but also observables pertinent to heavy-ion collisions, astrophysics, and more. Our online platform allows users to choose different descriptions (with different parametrizations), how these are connected, and what observables they reproduce. The platform is open for everyone, and all our code is open source.

Speaker: Veronica Dexheimer (Kent State University)

DexheimerGHP.pdf

80 Building Neutron Stars using MUSES Workflows

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, Chiral Effective Field Theory valid around saturation density, and the Chiral Mean Field Model valid beyond saturation density. These equations of state are matched together through the Synthesis module and coupled to a novel full-general-relativity solver module (QLIMR) that calculates neutron star properties. We also study the time evolution and bulk viscosity of the different equations of state using the Flavor Equilibration module.
MUSES is a powerful tool for neutron star and heavy-ion description, enabling fast and flexible computations that accommodate a wide range of physical models and parameters. Using MUSES Workflows, we present the first calculations of neutron star observables with these equations of state and show results for the flavor relaxation time from chiral effective field theory and chiral mean field.

Speaker: Mateus Reinke Pelicer (Kent State University)

Building Neutron Stars with the MUSES Calculation Engine.pdf

Workshop Banquet - Restaurant

Sunday, March 16

Parallel Session - Room 252A: J/Psi production (Chair: Latifa Elouadrhiri)

Convener: Latifa Elouadrhiri (Jefferson Lab)

81 J/psi photoproduction near threshold in CLAS12

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 hadronic states, such as pentaquark candidates, through their potential contributions to the J/psi -nucleon interaction.

Results from near-threshold J/psi photoproduction data collected in 2018 and 2019 with the CLAS12 detector at Jefferson Lab are presented. The measurement was performed using a high-energy electron beam impinging on a liquid hydrogen target. This analysis incorporates advanced lepton identification techniques, utilizing machine learning methods to reduce pion contamination, and applies targeted event selection criteria to isolate the J/psi signal.

Speaker: Mariana Tenorio Pita (Old Dominion University)

APS_GHP_MTenorio.pdf

82 J/ψ Near-threshold Photoproduction on the Proton and Neutron at CLAS12

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 radius.

The JLab based CLAS Collaboration, which uses the CEBAF Large Acceptance Spectrometer at 12 GeV (CLAS12), aims to measure the J/ψ near-threshold photoproduction cross section using both a proton and a deuteron target. The latter further offers the possibility of comparing the proton and neutron gluonic mass radii in a first measurement of the cross sections off a proton or neutron within the deuteron target. The analysis towards these measurements is well advanced and being finalized for publication.

This talk will describe the aims and experimental design for the measurement of J/ψ near-threshold photoproduction off the proton and neutron in deuteron with the CLAS12 detector along with preliminary first measurements of the J/ψ total and differential cross sections. The differential cross section in particular can be used to estimate the mass radius of the neutron which will be compared to previous estimates of the mass radius of the proton.

Speaker: Richard Tyson (Jefferson Lab)

JPsi_GHP_March2025.pdf

83 SpinQuest J/$\psi$ TSSA Study via Newly-built Polarized Target Assembly at Fermilab

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 contribute to resolve the nucleon spin puzzle. The experiment will also measure the $J/\psi$ azimuthal asymmetries, which are sensitive to the gluon Sivers function. Such studies are performed using a polarized target assembly deploying a split-pair 5 T superconducting magnet and a powerful cooling system based on the $^4$He evaporation refrigerator. The latter operates at 1 K through high-powered evaporation facilitated by a roots stack with a pumping rate of $\approx~$17,000 liters per hour. With such a setup, the expected average target polarization of $\approx$ 80\% (32\%) for NH$_3$ (ND$_3$) will be achieved based on the dynamic nuclear polarization technique. In this talk, an overview of the first run-period performance of the SpinQuest polarized targets will be presented alongside the ongoing efforts to study systematic effects of the $J/\psi$ Transverse Single Spin Asymmetry.

This work is supported in part by the U.S. DOE award $\#$: DE-FG02-07ER41528.

Speaker: Vaniya Ansari (Mississippi State University)

APS-GHP_March2025_Vaniya.pdf

84 Machine Learning approach to determine the transverse single spin assymetry in J/ψ production in SpinQuest experiment

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 involves initial-state gluons, TSSA measurements provide valuable information about gluon dynamics within the nucleon. The SpinQuest experiment (E1039) at Fermilab utilizes a 120 GeV unpolarized proton beam impinging on a polarized fixed target composed of NH$_3$ or ND$_3$. The primary goal is to extract the Sivers functions for light sea quarks in the kinematic range $0.1 < x_B < 0.5$. The analysis employs an event-mixing method to estimate combinatorial backgrounds and leverages machine learning techniques, including Gaussian Process Regressors (GPR), to efficiently model backgrounds using sidebands. We also use Bayesian iterative unfolding, in addition to GPR to correct detector inefficiencies. These measurements are critical for constraining the gluon Sivers function and provide a unique kinematic bridge between valence quark studies and the parameter space accessible in future Electron-Ion Collider (EIC) experiments. This talk will present the current status of the SpinQuest experiment and preliminary findings from beam commissioning data.

This work was supported in part by US DOE grant DE-FG02-94ER40847.

Speaker: Dr Chatura Kuruppu (New Mexico State University)

2025_03_10_APS_GHP_Talk_v3.pdf

Parallel Session - Room 252B: Collectivity and finite Temperature (Chair: Bjoern Schenke)

Convener: Bjoern Schenke (Brookhaven National Lab)

85 The Present and Future of Small-System Collectivity Search from STAR

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 through O+O collisions at RHIC, offering a unqiue opportunity to study the interplay between initial-state geometry and fluctuations. In the same year, STAR revisited d+Au collisions at RHIC, utilizing the detector’s extended pseudorapidity coverage ($|\eta| <$ 1.5) and (2.1 $< |\eta| <$ 5.1) to systematically study azimuthal correlations, focusing on their dependence on relative pseudorapidity ($\Delta\eta$).

The smallest system displaying collectivity observed at RHIC to date is p+Au. To examine even smaller systems, STAR has initiated a search for collectivity in photon-induced ($\gamma$+Au) processes by triggering on ultra-peripheral Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, corresponding to a maximum photon-nucleon center-of-mass energy of $W_{\gamma,N} \approx$ 34.7 GeV. Additionally, in 2024, STAR conducted its first dedicated effort to probe collectivity in high-multiplicity $p+p$ collisions, collecting high-statistics data at low luminosity at RHIC.

This talk will present STAR’s latest measurements of azimuthal correlations in O+O and d+Au collisions, the status of the collectivity search in $\gamma$+Au processes.We will also discuss the challenges, prospects, and future directions for collectivity studies using high-statistics data from the 2023–2025 RHIC runs in various small systems such as $\gamma$+Au, $p+p$, and the anticipated p+Au collisions.

Speaker: Prithwish Tribedy (Brookhaven National Lab.)

star_present_future_collectivity_aps_ghp2025_v4.pdf

86 The QCD static potential at finite temperature beyond leading order

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 screened potential, or because they become wide resonances. We calculate next-to-leading order corrections to the static potential using finite temperature perturbation theory and study their effect on the dissociation temperature of heavy quarkonia. We also study the influence of anisotropy on bound-state energies.

Speaker: Margaret Carrington (Brandon University)

Anaheim-2025-Carrington.pdf

87 Directed Flow of Protons and Anti-Protons in RHIC Beam Energy Scan II

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 interest as they offer sensitivity to both the contributions from
the transported quarks and also the medium generated component from the produced
quarks. Measurements of proton and net proton directed flow from BES-I have shown that
there is a non-monotonous dependence on collision energy. We will present
measurements of the directed flow of protons and anti-protons from the collision energies
of 7.7, 9.2, 11.5, 14.5, 17.3, 19.6, and 27 GeV Au+Au collisions, using high statistics BES-II
data from STAR. We will also present a decomposition of proton directed flow into a
medium generated component and a component ($v_{1}$ excess) attributed to transported
protons. The v1 excess component is found to show a simple scaling from a center of mass
energy of 200 GeV to ~10 GeV, but to break scaling below 10 GeV. The new results have
significantly reduced uncertainties compared to those from BES-I and also allow
differential measurements in centrality and transverse momentum. Measurements will be
compared to different model calculations and implications to the understanding of the
QCD phase structure and EoS of the medium will be discussed.

Speaker: Emilie Duckworth (Kent State University)

GHP_presentation_2025-03-14.pdf

88 --

Parallel Session - Room 252C: Heavy Flavors in Heavy Ion Collisions I (Chair: Dhanush Hangal)

Convener: Dhanush Hangal (Lawrence Livermore National Laboratory)

89 Charm Tetraquark Production by Intrinsic Charm

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 into the nature of the tetraquark candidates, whether as a bound meson pair or as a looser configuration of four individual partons which can influence their interactions in the nuclear medium, such as in heavy-ion collisions. The kinematic distributions of these states as a function of $y$ and $p_T$ are also studied. Previous investiagations [2-4] show that $J/\psi$ and $\overline D$ mesons produced from such states manifest themselves at forwrad rapidity and relatively high $p_T$. The extension to bottom tetraquark candidates is also considered.

[1] R. Vogt, Tetraquarks from Intrinsic Heavy Quarks,Phys. Rev. D in press, arXiv:2405.09018 [hep-ph].

[2] R. Vogt, Limits on Intrinsic Charm Production from the SeaQuest Experiment, Phys. Rev. C 103 (2021), 035204.

[3] R. Vogt, Energy dependence of intrinsic charm production: Determining the best energy for observation, Phys. Rev. C 106 (2022) 025201.

[4] Contribution from intrinsic charm production to fixed-target interactions with the SMOG Device at LHCb, Phys. Rev. C 108 (2023) 015201.

This work was performed under the auspices of the US DoE by LLNL under Contract DE-AC52-07NA27344 and supported by LDRD projects 21-LW-034 and 23-LW-036 and the HEFTY Collaboration.

Speaker: Ramona Vogt (LLNL/UC Davis)

GHP25_talk.pdf

90 Bottomonium suppression in \texorpdfstring{$p\,$}{p}-Pb collisions at the LHC energies

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 hot Quark-Gluon-Plasma (QGP) medium. To calculate the nuclear shadowing (nPDF effect), we use EPPS21 nPDFs. For the coherent energy loss and momentum broadening, we adopt the method developed by Arleo, Peigne, and collaborators. The 3+1D viscous hydrodynamic evolution of the quark-gluon plasma is modeled with anisotropic hydrodynamics. To evaluate bottomonium suppression within the QGP, we employ two methods: a next-to-leading order open quantum system framework formulated within potential nonrelativistic quantum chromodynamics (pNRQCD), and a semi-classical kinetic rate equation using perturbative and non-perturbative bottomonium reaction rates. We compare the suppression predictions from both methods. Finally, combining the CNM and HNM effects, we compute the nuclear modification factor ($R^\Upsilon_{pA}$) of $\Upsilon(nS)$ states as a function of rapidity $(y)$ and transverse momentum $(p_T)$. Then, we compare our results with experimental data from the ALICE, ATLAS, CMS, and LHCb Collaborations. Incorporating all these effects gives a reasonably accurate description of the experimental data, supporting the idea of hot and short-lived QGP formation in the min-bias $p$-Pb collisions at the LHC energies.

Speaker: Sabin Thapa (Kent State University)

GHP-APS2025-Sabin-Final.pdf

GHP-APS2025-Sabin-Final.pptx

91 Open heavy flavor physics studies for the Electron-Ion Collider

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 preserved once produced. This feature makes the heavy flavor product an ideal probe to study the transport properties of heavy quarks inside different nuclear media and to explore the heavy quark hadronization processes. A series of heavy flavor hadron and jet physics studies have been carried out in standalone simulations with parameterized EIC detector performance. We will present the projected nuclear modifications of heavy flavor jets and heavy flavor hadrons inside jets in $e+p$ and $e+A$ collisions at different center of mass energies with the projected integrated luminosities at the EIC. These EIC heavy flavor physics projections will be compared with recent theoretical calculations and we will discuss their impacts in extracting the flavor dependent fragmentation functions and revealing the flavor dependent parton energy loss mechanism in cold nuclear medium. These future EIC studies are expected to help constraining the initial- and final-state effects for similar measurements in $p+p$, $p+$A and A+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC).

Speaker: Dr Xuan Li (Los Alamos National Laboratory)

GHP2025_XuanLi_v2.pdf

92 Unresolved Questions in Cold Nuclear Matter

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 as nuclear parton distribution functions (nPDFs), medium-induced gluon radiation, and gluon saturation. The workshop aimed to develop a universal theoretical framework for interpreting experimental data across different collision systems and to highlight the potential of future Electron-Ion Collider (EIC) data. This talk will summarize the key outcomes of the workshop, including the identification of unresolved CNM questions and the definition of the most suitable observables to address them.

Speaker: Charles Joseph NAÏM (Stony Brook University (CFNS))

APS_GHP_NAIM.pdf

Parallel Session - Room 255B: TMD and GPD I (Chair: Daniel Pitonyak )

Convener: Daniel Pitonyak (Lebanon Valley College)

93 Phenomenological extraction of GPDs using machine learning

I will report on our current progress in phenomenological extraction of Generalized Parton Distributions (GPDs) utilizing neural networks and stochastic gradient descent optimization.

Speaker: Eric Moffat (Argonne National Lab)

Moffat_GHP_3-16-25.pdf

94 Progress on the simultaneous analysis of collinear and transverse momentum parton distributions

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-$b_T$ region, the TMD is dominated by perturbative contributions, which are described by the operator product expansion (OPE) through collinear PDFs and evolution, while the large-$b_T$ region is dominated by intrinsic nonperturbative transverse motion. Because of the explicit dependence of the PDF in the TMD, we perform a simultaneous extraction of collinear PDFs and nonperturbative TMD structures using the small-$q_T$ Drell-Yan (DY) and $Z$-boson production data as well as the collinear datasets such as those from recent JAM extractions. We analyze the impacts of the PDFs from the inclusion of the small-$q_T$ data.

Speaker: Patrick Barry (Jefferson Lab)

Barry_GHP.pdf

95 Quantum Entanglement Correlations in Double Parton Distributions

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 employ methods from quantum information theory to identify the presence of quantum (entanglement) vs. classical correlations between valence quarks in this model. Quantum correlations are found to be responsible for a suppression of the dPDF when $x_1 \ll x_2$. Finally, we show that the perturbative emission of a soft gluon from any of the valence quarks does not affect their reduced density matrix.

Speaker: Eric Kolbusz (Baruch College, CUNY)

EKolbusz_GHP2025_dpdfentanglement.pdf

96 Transverse Single-Spin Asymmetries in Inclusive DIS and SIDIS Production of Photons: Numerical Predictions using Models for Multi-Parton Correlators

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 nucleon is transversely polarized, a spin asymmetry AUT can be computed that is sensitive to quark-gluon-quark (qgq) correlators in the nucleon. These functions are not well known, especially in the region where the two quarks carry different momentum fractions. In this vein, we present here rigorously conducted numerical analyses of AUT for inclusive DIS as well as SIDIS with a final-state photon in order to test models for qgq functions and motivate future experiments. We compute AUT for both proton and neutron targets and compare to relevant DIS experimental data from the Jefferson Lab and HERMES as well as make predictions for DIS and “gamma-SIDIS” at the Electron-Ion Collider. In the latter case we thoroughly explore the phase space in order to identify the kinematics where the asymmetry could be measurable. This quantitative analysis of these models hopes to advance our understanding of quark-gluon-quark correlators, especially in anticipation of the EIC.

Speaker: Michael Harris (Lebanon Valley College)

Harris_Talk_GHP2025 (1).pdf

10:40 AM Coffee Break

Parallel Session - Room 252A: Gravitational Form Factors (Chair: David Frenklakh)

Convener: David Frenklakh (Brookhaven National Laboratory)

97 Gravitational Structure of the Proton

The study of the mechanical properties of the proton has been made possible through first measurement of the protons gravitational form factors (GFFs). This has been made possible due to remarkable progress over the past two decades driven by advances in the development of a theoretical framework based on the generalized parton distributions and the development of experimental techniques making use of large acceptance detectors operating at unprecedented high luminosities. These GFFs provide unique insights into the spatial distributions and mechanical properties of the proton, for both its quark content and its gluon content. There are 3 GFF for the quark part and 3 GFF for the gluon part, covering their respective mass and angular momentum distribution as well as the internal distribution of pressure and shear forces.  The GFFs therefore offer a much deeper understanding of the proton’s internal dynamics much beyond the measurement of the traditional charge and magnetic form factors.

This talk will review key theoretical and experimental developments, with a focus on ongoing and future studies enabled by the 12 GeV upgrade at Jefferson Lab. on its mechanical structure.

Looking ahead, planned upgrades at Jefferson Lab, along with the future Electron-Ion Collider (EIC), promise further breakthroughs. Enhanced luminosity and detector capabilities will enable more precise extractions of the GFFs, advancing our understanding of the QCD dynamics that shape nucleon structure.

Speaker: Latifa Elouadrhiri (Jefferson Lab)

GHP2025.pptx

98 Gravitational Form Factors in GPD Models

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 uncertainties of the extraction, and also comment on the possibility to extend to other exclusive processes.

Speaker: Yuxun Guo (Lawrence Berkeley National Lab)

APS_GHP_YuxunGuo_2025.pdf

99 Gravitational Form Factors in Holographic QCD

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 can be studied via first-principles calculations in lattice QCD as well as holographic QCD models, with remarkable consistency observed between the two approaches.

This talk will focus on the computation of gluonic gravitational form factors within holographic QCD, emphasizing the interplay between the $A$-term and $D$-term contributions. These form factors are shown to effectively capture the nucleon's mass distribution, pressure, and shear. Furthermore, we will discuss the recent experimental extraction of the tensor ($A$-term) and scalar ($D$-term) form factors using the holographic scattering amplitudes and data from JLab's $J/\psi-007$ experiment, particularly in the near-threshold photoproduction of $J/\psi$ on the proton. The holographic predictions not only align well with lattice QCD results but also provide deeper insights into the gluonic mass radius and the nucleonic pressure and shear profiles. These findings underscore the profound connections between holographic duality and non-perturbative QCD dynamics, contributing to our understanding of the quantum origins of visible mass in the universe.

By highlighting these theoretical developments and their experimental validation, this talk aims to illuminate the potential of holographic approaches in advancing QCD phenomenology.

Speaker: Dr Kiminad Mamo (William and Mary)

HGFF_GHP2025_Mamo.pdf

100 Do gravitational form factors describe forces inside hadrons?

Gravitational form factors parametrize the energy-momentum tensor of composite systems, and characterize the density and flow of energy and momentum in these systems. This past decade has seen a blossoming of interest in and diversity of views on spatial distributions of mechanical properties, especially following recent empirical extractions of gravitational form factors at Jefferson Lab. A salient question in these discussions is whether momentum flux densities, and the D-term in particular, furnish distributions of stresses (such as pressure and shear forces). In this talk I will explain the basic formalism relating form factors to spatial densities and the energy-momentum tensor to stresses, summarize the views that exist in the literature, and conclude with a new perspective that emphasizes the importance of the cbar form factor in characterizing forces inside hadrons.

Speaker: Adam Freese (Jefferson Lab)

main.pdf

Parallel Session - Room 252B: Mapping out QCD (Chair: Richard Tyson)

Convener: Richard Tyson (Jefferson Lab)

101 Interpreting u-Channel Scattering Cross Sections

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 distributions in the transverse plane. The less well-understood $u$-channel production is modeled by a baryon-exchange trajectory. The transformation of $u$-channel cross sections into the transverse plane may likewise provide insight on the distribution of baryon number within the proton. We discuss these interpretations using existing $u$-channel cross section data, and prospects for expanding on this data at the future Electron-Ion Collider will be assessed.

Speaker: Zachary Sweger (UC Davis)

Sweger_GHP_2025.pdf

102 Probing the nature of baryon number carrier through chemical potential differences in isobar collisions and net-hyperon yields dependence on beam energy

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 the chemical potential differences ($\Delta\mu = \mu_\text{Zr+Zr} - \mu_\text{Ru+Ru}$) between isobaric $_{44}^{96}$Ru+$_{44}^{96}$Ru and $_{40}^{96}$Zr+$_{40}^{96}$Zr collision systems at $\sqrt{s_{NN}}=200$GeV, based on charged particle yields in these collisions and electric charge difference ($\Delta Q$) between the two recently measured by the STAR collaboration. Utilizing Bayesian inference with THERMUS thermal model, we show that baryon and strange chemical potential differences ($\Delta \mu_B$ and $\Delta \mu_S$) are positive, while $\Delta \mu_Q$ is negative across all centralities. We find that $\Delta\mu_B/\Delta\mu_Q=-0.96\pm0.02$ in head-on collisions, which is close to the expected value of -1 for decoupled electric charge carried by quarks and baryon number. Furthermore, the dependence of mid-rapidity hyperon yields on beam rapidity demonstrates flavor independence, with $\Lambda$, $\Xi$, and $\Omega$ baryons exhibiting similar transport behavior. This is also consistent with the baryon junction picture as a junction is composed of flavorless gluons and the resultant baryon formed around the junction should be flavor blind. These results challenge the conventional assumption about baryon number being carried by quarks.

Speaker: Chun Yuen Tsang (Kent State University)

APS-GHP-meeting.pdf

103 --

104 --

Parallel Session - Room 252C: Heavy Flavors in Heavy Ion Collisions II (Chair: Ramona Vogt)

Convener: Ramona Vogt (LLNL/UC Davis)

105 Generative AI for High-Energy Heavy-Ion Experiments

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 computational costs of scientific simulations.
However, diffusion models, which have proven highly effective for generating high-quality text-to-image translations in industry, remain largely underexplored in high-energy heavy-ion physics.

This work represents the first application of diffusion models in this field, opening new possibilities for simulation techniques. We apply denoising diffusion probabilistic models (DDPMs) for full-detector, whole-event simulations in high-energy heavy-ion experiments [1]. Using Geant4-simulated HIJING events with the sPHENIX detector geometry, we compare the performance of DDPMs with that of GANs. Our results demonstrate that DDPMs not only deliver superior fidelity over GANs but also achieve over 100 times faster simulation speeds compared to Geant4, marking a significant advancement in accelerating event simulations for collider physics.

Additionally, we utilize unpaired image-to-image translation models for jet background subtraction in heavy-ion collisions. UVCGAN [2], a CycleGAN-based model, effectively isolates jets from the combinatorial background, with successful applications demonstrated at both the Relativistic Heavy Ion Collider and the Large Hadron Collider.

[1] Y. Go, D. Torbunov, et al., "Effectiveness of denoising diffusion probabilistic models for fast and high-fidelity whole-event simulation in high-energy heavy-ion experiments," Phys. Rev. C 110, 034912 (2023), arXiv:2406.01602
[2] D. Torbunov, et al., "UVCGAN v2: An Improved Cycle-Consistent GAN for Unpaired Image-to-Image Translation," arXiv:2303.16280

Speaker: Yeonju Go (Brookhaven National Laboratory)

20250316_GHP_YeonjuGo.pdf

106 Study of the relative mass and width of the Z boson dimuon decay, as a function of centrality, in PbPb collisions with CMS

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 present the status of an ongoing study of the relative change of the mass and width with centrality of the Z boson, from Pb-Pb collisions at √sNN=5.02 TeV, using the CMS detector.

Speaker: Frank Gonzalez (University of California, Davis)

APSGHP_FrankGonzalez_Mar16_2025.pdf

107 Highlights of Heavy Flavor Physics Studies in the PHENIX experiment at RHIC

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 into the properties of the quark-gluon plasma (QGP), cold nuclear matter (CNM) effects in small collision systems, and the structure and dynamics of quarks and gluons within polarized protons.
In this presentation, I will showcase selected heavy-flavor measurements from PHENIX in heavy-ion and polarized p+p/A collisions, with an emphasis on recent results. Topics will include studies of QGP properties, the influence of CNM effects, and their implications for nucleon structure and QCD dynamics. These findings highlight the ongoing contributions of PHENIX experiment at RHIC to advancing our understanding of strong interactions and the nuclear matter.

Speaker: Dr Ming Liu (Los Alamos National Lab)

HeavyFlavor-physics-PHENIX-GHP-032025-final.pdf

108 --

Parallel Session - Room 255B: TMD and GPD II (Chair: Eric Moffat)

Convener: Eric Moffat (Argonne National Lab)

109 Global QCD Analysis of Proton's Transverse Structure through TMDs and DiFFs

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.

Speakers: Christopher Cocuzza (Temple University), Daniel Pitonyak (Lebanon Valley College)

Cocuzza_GHP2025.pdf

110 Progress toward TMD factorization at next-to-leading power

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 leading power (NLP). We emphasize the role of renormalization group consistency as a necessary condition establishing TMD factorization at NLP. We also discuss the criteria of matching large and small transverse momentum of the cross section in relation to establishing TMD factorization at NLP. Establishing TMD factorization at NLP is crucial for performing 3D imaging of hadrons in current and future DIS experiments, and thus for ongoing global analyses. In this context, we focus on the cosφ modulation—known as the Cahn effect—which highlights the central role of partonic intrinsic transverse momentum in explaining the transverse momentum spectrum in SIDIS for meson production.

Speaker: Leonard Gamberg (Penn State Berks)

GHP_25_Gamberg_f.pdf

111 Nucleon Parton Distribution Functions from Boosted Correlations in the Coulomb Gauge

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.

Speaker: Jinchen He (University of Maryland, College Park)

GHP_2025_Jinchen_modified.pdf

112 Spin physics highlights from PHENIX

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 the proton spin while the longitudinal spin asymmetry of W bosons helped uncover a nonzero polarized sea quark asymmetry. Transverse spin asymmetries at central rapidity of direct photons, light mesons, and open heavy flavor provided significant constraints on spin-momentum correlations between protons and their constituent gluons. At forward rapidity, large transverse spin asymmetries of charged hadrons and light mesons highlighted the substantial impact of the initial- and final-state quark-gluon correlation functions. Nuclear effects in spin physics were also studied through measurements of transverse spin asymmetries from transversely polarized $p^{\uparrow}+A$ collisions. While little impact is seen at central rapidity, large nuclear effects observed at forward rapidity remain a mystery phenomenologically. In this presentation, I will discuss these recent highlights of spin physics from PHENIX and how they help inform our understanding of the field.

Speaker: Devon Loomis (University of Michigan)

Loomis_GHP2025.pdf

12:40 PM Lunch Break

Award Session - Room 255B: II (Chair: Bernd Surrow)

Convener: Bernd Surrow (Temple University)

113 Correlations and collectivity from small to large systems

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 at RHIC and the LHC.

Linking these phases I will describe how a global Bayesian analysis can leverage a wide variety of such experimental data to gain knowledge about the QGPs intrinsic properties. I will then highlight some recent progress in our understanding of in particular the shapes of small and large ions. This includes the neutron skin of Pb-208, triaxiality of Xe-129 and (upcoming) light ion collisions of O-16 and possibly Ne-20 at RHIC and LHC.

Speaker: Wilke van der Schee (CERN / Utrecht University)

Talk_APS2025.pptx

114 Aspects of the chiral and partonic structure of the nucleon (2023 GHP Fellow)

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 fragmentation functions, the understanding of high-energy transverse single-spin asymmetries, partonic Wigner functions, as well as the transversity distributions and the tensor charges.

Speaker: Andreas Metz (Physics Department, Temple University, Philadelphia)

GHP_meeting_Metz.pdf

115 Overview of the Jefferson Lab Hall A SBS form factor experiments (2024 GHP Fellow)

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 neutron form factor experiments used the BigBite Spectrometer to detect electrons and the Super BigBite Spectrometer to detect the quasi-elastically scattered neutrons. The neutron's magnetic form factor was measured up to $Q^2$ = 13.5 GeV$^2$. The neutron's electric form factor was measured up to $Q^2$ = 10 GeV$^2$. In early 2025, the proton's electric form factor will be measured up to $Q^2$ = 12 GeV$^2$ with BigBite Spectrometer replaced by a combination of large acceptance scintillator array and electron calorimeter for the detection of electrons and the SBS detecting the elastically scattered protons. The recent experiments will be discussed in context of previous nucleon form factor experiments and theoretical calculations.

Speaker: Mark Jones (Jefferson Lab)

MKJ-GHP-talk.pdf

3:40 PM Coffee Break

Award Session - Room 255B: II (Chair: Bjoern Schenke)

Convener: Bjoern Schenke (Brookhaven National Lab)

116 Explainable AI (XAI) based path to the simplification of deeply virtual; exclusive scattering amplitudes (2024 GHP Fellow)

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 proton’s interior can be also captured by introducing two-particle spatial density distributions. The latter yield the relative position of quarks and gluons with respect to one another in the transverse plane, providing a measure of the amount of correlations in the particles’ motion. I will illustrate a pathway to the extraction of these quantities from data, that leverages explainable AI to advance our understanding
the observables for deeply virtual exclusive experiments in terms of their fundamental quark and gluon structure.

Speaker: simonetta liuti (university of virginia)

liuti_GHP25.pptx

117 Experimental access of high-multiplicity photo-nuclear interactions and a novel investigation of collective phenomena in this system (2024 APS GHP Dissertation Award)

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 mass energies of 1 TeV. One interesting question is whether photonuclear collisions are characterized by a momentary hot deconfined QCD-mediated state of matter, which is the dominant paradigm of nucleus-nucleus collisions at similar energies. This talk details the first dedicated collection and analysis of high-multiplicity photon-Pb collisions at the LHC. Results are presented for a search for signatures of an evolving QCD medium (commonly modeled with relativistic hydrodynamics) and other basic properties of photon-Pb collisions. Significant hydrodynamic-like behavior is observed and theorized to arise from the photon fluctuations into a di-quark hadronic states which are resolved by the Pb target, resembling proton-nucleus collisions where similar signatures have also been detected. The measurements of photonuclear collisions are compared to proton-Pb collisions as well as theoretical models based on hydrodynamics and alternatively initial-state momentum anisotropy. This work demonstrates the accessibility and utility of photonuclear collisions for a broad range of research in hadron physics as well as foreshadows and compliments research at future electron-ion colliders.

Speaker: Blair Seidlitz (University of Colorado at Boulder)

BSeidlitz_GHP25.pdf

118 Exploring Hadron Structure Through Monte-Carlo Fits and Model Calculations (2025 APS GHP Dissertation Award)

We have performed several global Quantum Chromodynamics (QCD) analyses to provide information on the one-dimensional (1D) structure of the proton using the latest experimental data available. Among the mysteries that remain within the proton, we provide insight on the nonperturbative nature of the proton’s sea quarks, for both cases where the proton is unpolarized and longitudinally polarized. We also bring new information on the “proton spin puzzle,” which concerns the delegation of the proton’s spin into its constituent quarks and gluons. We shed light on the proton’s transversely polarized structure, where current results from global QCD analyses and lattice QCD seemingly fail to paint a consistent picture. Our analyses also reveal a new feature of nuclear effects within light, highly asymmetric nuclei such as helium and tritium. Finally, we perform derivations in a spectator diquark model to glean information on the proton’s 3D structure, and calculate moments that can be used in future lattice QCD studies.

Speaker: Christopher Cocuzza (College of William & Mary)

Dissertation_Award.pdf

Dissertation_Award.pdf

5:30 PM Break

GHP Business Meeting - Room 255B: (Chair: Bernd Surrow)

Convener: Bernd Surrow (Temple University)

119 GHP Overview

Speaker: Bjoern Schenke (Brookhaven National Lab)

Schenke-GHP.pdf

120 DOE

Speaker: Sharon Stevenson

121 Award Ceremony

Speaker: Bernd Surrow (Temple University)

3_APS_GHP2025_Award_Session FINAL.pdf

122 Jefferson Lab

Speaker: David Dean (TJNAF)

20250316 News from Jefferson Lab.pdf

123 BNL

Speaker: Abhay Deshpande (Stonybrook)

01 BNL Present.pdf

01 BNL Present.pptx

124 EIC

Speaker: Abhay Deshpande (Stonybrook)

02 EIC Present.pdf

02 EIC Present.pptx

125 Treasurer report

Speaker: Christian Weiss (Jefferson Lab)

ghp25_treasurer.pdf

126 PRC/APS Journals

Speaker: Ramona Vogt (LLNL/UC Davis)

PRC_discussion_RV.pdf

127 Closing

Speaker: Bernd Surrow (Temple University)

9_APS_GHP2025_Closeout.pdf