XIIth Meeting on Lattice Parton Physics from Large Momentum Effective Theory (LaMET 2025)

Oct 8, 2025, 8:00 AM → Oct 10, 2025, 6:00 PM America/New_York

CFNS, Peter Paul Seminar Room, C 120 Physics Building (Stony Brook University/Online)

This event may be attended in person, or virtually using Zoom.

This event is part of the CFNS Workshop/Ad-Hoc Meeting series. See the CFNS conferences page for other events.

---

The XIIth Meeting on Lattice Parton Physics from Large Momentum Effective Theory (LaMET 2025) will be officially hosted by the Center for Frontiers in Nuclear Science (CFNS) at Stony Brook University, Stony Brook, NY, during Oct 8-10, 2025. This meeting aims to bring together physicists interested in LaMET and other theoretical approaches with their applications to lattice QCD in the calculation of parton physics.

In-person participation is strongly recommended, but remote participation via Zoom will also be possible. If you plan to come in person and need an invitation letter to apply for a US visa, please contact Ross Corliss <ross.corliss@stonybrook.edu>.

Important deadlines:

Abstract submission: Sep 12, 2025, 11:59 PM EDT.

Registration: Sep 19, 2024, 11:59 PM EDT.

Each talk will tentatively be given 20 to 30 minutes for presentation and 5 minutes for questions. Talks based on newly published or ongoing works are preferred.

---

Previous LaMET Workshops

University of Maryland, College Park, US, August 11-14, 2024

University of Regensburg, German, July 24-26, 2023

Argonne National Laboratory, US, December 1-3, 2022

CNF (SURA), virtual meeting, US, December 7-9, 2021

CNF (SURA) and CFNS (Stony Brook U), virtual Meeting, US, September 7-11, 2020

Brookhaven National Laboratory, US, April 17-19, 2019

University of Maryland, College Park, US, April 6-8, 2018

Peking University, China, July 14-16, 2017

Shanghai Jiao Tong University, China, December 17-18, 2016

University of Maryland, College Park, US, March 30 - April 2, 2014

Shanghai Jiao Tong University, China, November 2-4, 2012

---

This workshop is hosted at and supported by

Wed, October 8

8:50 AM → 9:00 AM Welcome

9:00 AM → 10:30 AM Session I

9:00 AM The First Gluon PDF from Large Momentum Effective Theory

We report the first nucleon gluon parton distribution function (PDF) using Large-Momentum Effective Theory (LaMET). We compute the matching coefficients for the gluon operator with the best signal to perform hybrid-renormalization and matching to the lightcone at the one-loop level. We demonstrate that with the proper Wilson coefficients in place, the counterterms for the renormalization are independent of the hadron and mass within statistical error. Using the resulting renormalization, we then compute the nucleon PDF using a HISQ ensemble generated by the MILC collaboration with $N_f = 2 + 1 + 1$, $a \approx 0.12$ fm, with valence pion masses of 310 and 690 MeV and two gauge link smearing techniques. Despite the physics effects of the heavier than physical pion masses and gauge link smearing, this calculation provides excellent proof of principle and compares reasonably with selected global fit results. We also report on preliminary results towards computing the gluon PDF from Coulomb gauge fixed correlators.

Speaker: William Good (Michigan State University)

9:20 AM Toward Continuum-Extrapolated Gluon PDFs from LaMET with Self-Renormalization

We report on recent progress in calculating gluon parton distribution functions (PDFs) using Large-Momentum Effective Theory (LaMET) combined with a self-renormalization approach to address the renormalization of gluon operators. Our study uses three HISQ ensembles with lattice spacings of $a = \{0.0888, 0.1207, 0.1510\}$ fm and a valence pion mass of $M_\pi \approx$ 310 MeV, with continuum extrapolation across these lattice spacings to control discretization effects. The resulting gluon PDFs will be compared with selected global fits to assess consistency and explore physical implications.

Speaker: Alex NieMiera (Michigan State University)

9:40 AM Unpolarized gluon parton distribution from lattice QCD in the continuum limit

We report a lattice QCD calculation of the nucleon gluon parton distribution function in the continuum-limit, employing large-momentum effective theory. The calculation is carried out on the 2+1 flavour CLQCD ensembles with three lattice spacings a = {0.105, 0.0897, 0.0775} fm and pion mass of approximately 300 MeV, covering nulceon momenta up to 1.97 GeV. Distillation technique is applied to improve the signal of two-point correlators. We then use the state-of-the-art hybrid renormalization and one-loop perturbative matching scheme, and extrapolate the results to continuum limit and infinite momentum limit.

Speaker: Chen Chen (Institute of Modern Physics)

10:05 AM Total Gluon Helicity from Lattice

We use the ensemble C24P29 provided by the CLQCD collaboration, insert the topological current using the proton external state of the momentum smear under the Coulomb gauge of the $5-\mathrm{HYP}$ smear, extract the matrix elements to calculate the gluon helicity under lattice QCD, and the calculation proves that different components of the topological currents $𝐾^\mu$ can be used to give consistent results within the error range. In addition, we use the $\mathrm{RI/MOM}$ renormalization scheme, consider the mixing of gluon and quark helicity, and extract the renormalization constant to give the gluon helicity result under $\overline{\mathrm{MS}}$ scheme.

Speaker: Dian-Jun Zhao (CUHK(Shenzhen))

10:30 AM → 11:00 AM Coffee Break

11:00 AM → 12:15 PM Session II

11:00 AM GUMP1.0 proton GPD analysis including lattice QCD input

I will present the first global proton GPD analysis by Y. Guo et al, with
lattice QCD input. I also comment on LaMET calculations of GPDs.

Speaker: Xiangdong Ji (U. Maryland)

11:25 AM GPDs from Lattice QCD with Asymmetric Momentum Transfer: Unpolarized Quarks at Nonzero Skewness

This work presents a generalization of the asymmetric-frame approach to generalized parton distributions that explicitly includes longitudinal momentum transfer, enabling studies at nonzero skewness $\xi$. The method reorganizes nucleon matrix elements into Lorentz-invariant, frame-independent amplitudes -- an extension of our earlier $\xi=0$ work in unpolarized, helicity, and transversity sectors -- with a wide range of accessible kinematics in a single lattice calculation, which allows a mapping of GPDs from the lattice. We validate the general-$\xi$ formalism using two sets of momentum transfer: with combined transverse and longitudinal transfer and with purely longitudinal transfer, the latter reducing the number of independent amplitudes. From coordinate-space correlators, we determine the invariant amplitudes and construct the unpolarized GPDs $H$ and $E$; we then build quasi-distributions and perform matching to the light cone. The talk will also clarify the main hurdles specific to $\xi\neq0$.

Speaker: Manuel Colaço (Adam Mickiewicz University)

11:50 AM Resummation for Lattice QCD Calculation of Generalized Parton Distributions at Nonzero Skewness

Large-momentum effective theory (LaMET) provides an approach to directly calculate the $x$-dependence of generalized parton distributions (GPDs) on a Euclidean lattice through power expansion and a perturbative matching. When a parton's momentum becomes soft, the corresponding logarithms
in the matching kernel become non-negligible at higher orders of perturbation theory, which requires a resummation. But the resummation for the off-forward matrix elements at nonzero skewness $\xi$ is difficult due to their multi-scale nature. In this work, we demonstrate that these logarithms are important only in the threshold limit, and derive the threshold factorization formula for the quasi-GPDs in LaMET. We then propose an approach to resum all the large logarithms based on the threshold factorization, which is implemented on a GPD model. We demonstrate that the LaMET prediction is reliable for $[-1+x_0,-\xi-x_0]\cup[-\xi+x_0,\xi-x_0]\cup[\xi+x_0,1-x_0]$, where $x_0$ is a cutoff depending on hard parton momenta. Through our numerical tests with the GPD model, we demonstrate that our method is self-consistent and that the inverse matching does not spread the nonperturbative effects or power corrections to the perturbatively calculable regions.

Speaker: Rui Zhang (argonne national laboratory)

12:15 PM → 1:30 PM Lunch Break

1:30 PM → 3:30 PM Session III

1:30 PM Momentum Flow Mechanisms and Forces on Quarks in the Nucleon

Momentum conservation in the nucleon is examined in terms of continuous flow of the momentum current density (or in short, momentum flow), which receives contributions from both kinetic motion and interacting forces involving quarks and gluons. While quarks conduct momentum flow through their kinetic motion and the gluon scalar (anomaly) contributes via pure interactions, the gluon stress tensor has both effects. The quarks momentum flow encodes the information of the force density on them, and the momentum conservation allows to trace its origin to the gluon tensor and anomaly ("negative pressure" potential). From state-of-the-art lattice calculations and experimental fits on the form factors of the QCD energy-momentum tensor, we exhibit pictures of the momentum flow and forces on the quarks in the nucleon. In particular, the anomaly contributes a critical attractive force with a strength similar to that of a QCD confinement potential.

Speaker: Chen Yang (University of Maryland, College Park)

1:55 PM Transversity GPDs from Lattice QCD

Traditional approaches on studying the $x$-dependence through Large Momentum Effective Theory (LaMET) for GPDs are calculating non-local matrix elements in the symmetric frame. Recently, the novel approach of calculating GPDs in the asymmetric frame through a parameterization of the matrix elements, using Lorentz-invariant amplitudes, has been conducted for the unpolarized (PhysRevD.106.114512) and helicity (PhysRevD.109.034508) cases. Here, we extend our work to the twist-2 tensor case, where we calculate the 4 GPDs: $H_T$, $E_T$, $\tilde{H}_T$, and $\tilde{E}_T$. This is done for a momentum boost of $P_3$ = 1.25 GeV in the direction of the Wilson line, with a momentum transfer square $-t \in [0.17, 2.29] ~\mathrm{GeV}^2$. The calculations for this work use an $N_f$ = 2+1+1 ensemble of twisted mass fermions with a clover improvement. The quark masses give a pion mass of roughly 260 MeV.

Speaker: Joshua Miller

2:15 PM Updates on gluon GPDs and the hadronic structure of the photon from lattice QCD

We present updates on gluon GPDs and the hadronic structure of the photon from lattice QCD. The challenges in calculating gluon GPDs will be discussed, along with preliminary results for matrix elements probing the nonperturbative structure of the resolved photon. The lattice QCD calculation of the nonperturbative structure of the photon is being performed on the RBC/UKQCD domain-wall fermion ensembles.

Speaker: Raza Sufian (New Mexico State University & BNL)

2:40 PM Moments of Pion GPDs from Lattice QCD at Zero and Nonzero Skewness

We present a lattice QCD study of the moments of the pion generalized parton distributions (GPDs) at both zero and nonzero skewness. The calculations are performed at a lattice spacing of 0.04 fm with a pion mass of 300 MeV, using boosted states up to Pz = 2.43 GeV and momentum transfers reaching 2.75 GeV^2. We extract the generalized form factors (GFFs) associated with the first few moments from nonlocal correlation functions using non-singlet operators. Nonperturbative renormalization and matching are carried out in the ratio scheme, and the data are analyzed through combined fits over multiple kinematics. The zero-skewness results agree with earlier studies, while the nonzero-skewness data are crucial for verifying polynomiality and extracting higher-order GFFs. Finally, the extracted moments are evolved with next-to-next-to-leading order renormalization group resummation, improving the control of perturbative uncertainties.

Speaker: Fei Yao

3:05 PM Nucleon Form Factors with Domain Wall Fermions at Physical Pion Mass

We present results for the vector and axial form factors of the isovector nucleon in $2+1$ flavour lattice QCD with Domain Wall fermions. Our pion mass is physical and the lattice spacing is $a=0.114$ fm. We extract the Dirac and Pauli form factors as well as the axial and induced pseudoscalar form factors, and study their momentum transfer dependence over the range $0.05 \lesssim Q^2 \lesssim 0.45\, \text{GeV}^2$. Additionally, we present results for the axial charge $g_A$, and electromagnetic and axial radii. We also discuss implications of the Partially Conserved Axial Current relation in the extraction of the axial form factor.

Speaker: Liam Hockley (New Mexico State University)

3:30 PM → 4:00 PM Coffee Break

4:00 PM → 5:30 PM Discussion

Thu, October 9

9:00 AM → 10:30 AM Session IV

9:00 AM Ill-Posedness in Limited Discrete Fourier Inversion for Quasi Distributions in LaMET

We systematically investigated the inverse discrete Fourier transform of quasi-distributions from the perspective of inverse problem theory. Mathematically, we have demonstrated that this transformation satisfies two of Hadamard’s well-posedness criteria, existence and uniqueness of the solution, but critically violates the stability requirement. To address this instability, we employed and compared four classical and widely-used inversion methods: Tikhonov regularization, the Backus–Gilbert method, Bayesian inference, and neural networks. The efficacy of these approaches is validated through controlled toy model studies and real lattice QCD results for quasi-distribution amplitudes. The reconstructed solutions are consistent with those from the physics-driven \lambda-extrapolation method. Our analysis shows that the inverse Fourier problem within the large-momentum effective theory (LaMET) framework constitutes a moderately tractable ill-posed problem. Except for the Backus–Gilbert method which has been shown mathematically to be flawed, all other approaches successfully reconstruct the quasi-distributions in momentum space. Depending on the specific behavior of the quasi-distribution data, it is essential to adopt tailored strategies for data processing and to systematically estimate the associated systematic uncertainties.

Speaker: Ao-Sheng Xiong (Lanzhou University)

9:20 AM Renormalon effect of quasi-PDF in gradient flow formalism

The gradient flow has emerged as a powerful tool to enhance the Large Momentum Effective Theory (LaMET) program, offering both conceptual and practical advantages in lattice QCD studies of hadronic structure. In this report, I present our recent progress in applying the gradient flow to baryon light-cone distribution amplitudes (LCDAs) and quasi-parton distribution functions (quasi-PDFs). For baryon LCDAs, a hybrid renormalization scheme combining the ratio method with gradient flow eliminates logarithmic divergences and enables high-precision determination of nonperturbative amplitudes. For quasi-PDFs, explicit bubble-chain calculations reveal that the gradient flow removes ultraviolet renormalons while significantly deforming the infrared renormalon structure, thereby modifying the pattern of higher-twist corrections. These developments highlight the dual role of gradient flow: it both improves numerical stability in lattice computations and reshapes our understanding of renormalization and power corrections in LaMET. Together, they establish gradient flow as a key ingredient in advancing precision studies of partonic structure from first principles.

Speaker: Jialu Zhang (Shanghai Jiao Tong University)

9:40 AM Regularization Prescription for the Mixing Between Nonlocal Gluon and Quark Operators

It is well-known that in the study of mixing between nonlocal gluon and quark bilinear operators there exists an ambiguity when relating coordinate space and momentum space results, which can be conveniently resolved through Mellin moments matching in both spaces. In this work, we show that this ambiguity is due to the lack of a proper regularization prescription of the singularity that arises when the separation between the gluon/quark fields approaches zero. We then demonstrate that dimensional regularization resolves this issue and yields consistent results in both coordinate and momentum space. This prescription is also compatible with lattice extractions of parton distributions from
nonlocal operators.

Speaker: Zhuoyi Pang

10:05 AM Bjorken and threshold limits of a quasi-PDF-like structure function in the 2D large-N Gross-Neveu model

In this talk, we will present the exact expansions at the next-to-leading order in the $1/N$ expansion for a space-like structure function in the 2D large-N Gross-Neveu model, in the Bjorken and the threshold limits.

The space-like structure function is similar to the lattice-calculable quasi-PDFs. As such, the exact expansion in the Bjorken limit allows a non-trivial first principle verification of the standard factorization conjectures for such quantities, in terms of the perturbative coefficient functions in the presence of infinitely-many perturbative orders, and the non-perturbative PDF-like scaling functions. The expansions are performed to all powers, in a way that manifests the renormalon conspiracy across different powers, between the perturbative coefficient functions and the non-perturbative scaling functions. Convergence properties of the expansions, as well as the resurgence relation between the threshold and the "Regge'' asymptotics will also be discussed.

Speaker: Yizhuang Liu (Jagiellonian University)

10:30 AM → 11:00 AM Coffee Break

11:00 AM → 12:15 PM Session V

11:00 AM First-Principle Calculation of Collins-Soper Kernel from Quasi-Transverse-Momentum-Dependent Wave Functions

We present a lattice QCD calculation of the Collins-Soper kernel, which governs the rapidity evolution of transverse-momentum-dependent (TMD) distributions, using Large Momentum Effective Theory (LaMET). Quasi-TMD wave functions are computed with three meson momenta on CLQCD configurations (multiple lattice spacings and pion masses) employing clover quarks and varied hadronic states. HYP smearing is applied to staple-shaped gauge links and Wilson loops to enhance signal-to-noise ratios. Divergences are systematically addressed: linear divergences via Wilson-line renormalization and logarithmic divergences through a self-renormalization-inspired scheme.

By systematically controlling the sources of systematic uncertainties, we determine the Collins–Soper kernel up to transverse separations of 1 fm, followed by extrapolations to the large-momentum limit, the continuum limit, and the physical pion mass. This study delivers essential inputs for soft functions and precision analyses of TMD physics, thereby advancing first-principles QCD in the domain of high-energy phenomenology.

Speaker: Jin-Xin Tan (Shanghai Jiao Tong University)

11:25 AM Nucleon PDFs 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, helicity, and transversity 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)

11:50 AM Pion and Proton TMDPDFs from Coulomb-Gauge Quasi-TMDs

In this talk, we report our recent lattice QCD calculations of transverse-momentum-dependent parton distribution functions (TMDPDFs) for pion and proton using the Coulomb-gauge quasi-TMD framework. For the pion, we determine the valence-quark TMDPDF along with the intrinsic soft function and Collins–Soper kernel, showing consistency with perturbation theory at short transverse separations and with phenomenological fits at moderate momentum fractions. For the proton, we report the first lattice results of isovector helicity and flavor-dependent unpolarized TMDPDFs at physical quark masses using domain-wall fermions. Scale-independent ratios allow direct comparison with global fits, revealing similar helicity and unpolarized distributions at moderate x and only mild flavor dependence. These studies demonstrate the practicality of the Coulomb-gauge approach and provide nonperturbative benchmarks for global analyses and future experiments at the EIC.

Speaker: XIANG Gao

12:15 PM → 1:30 PM Lunch Break

1:30 PM → 3:30 PM Session VI

1:30 PM "From quark to gluon Collins–Soper kernels and bT-dependent LaMET matching

In this talk, progress in determining the quark Collins–Soper kernel using lattice QCD will be presented as a blueprint for the ongoing gluon kernel determination — to be discussed in the companion talk by Yang Fu.
Numerical results for the quark kernel will also be used to motivate the development of a convolutional transverse-scale–dependent LaMET matching, tailored to the intermediate regime — encountered in lattice QCD calculations — where hadronic boost is comparable to transverse momentum.

Speaker: Artur Avkhadiev (Argonne National Laboratory)

1:55 PM Gluon Collins-Soper kernel from lattice QCD

We will present the first lattice QCD calculation of gluon Collins-Soper kernel, which relates the transverse momentum-dependent gluon parton distribution functions at different energy scales.

Speaker: Yang Fu (MIT)

2:15 PM Measurement of the Collins-Soper kernel on the lattice using the auxiliary field representation of the Wilson line

The Collins-Soper (CS) kernel may be obtained through the TMD soft function by formulating the Wilson line in terms of 1-dimensional auxiliary fermion fields on the lattice. Our computation takes place in the region of the lattice that corresponds to the “spacelike” region in Minkowski space, i.e., Collins' scheme. We explore two methods for obtaining the CS kernel. The "ratio method"; which would allow us to obtain the soft function as well as the CS kernel. And the "double ratio"; which allows us to achieve a high degree of statistical precision, but only produces the CS kernel. The matching of our result to Minkowski space is achieved through the mapping of the auxiliary field directional vector to the Wilson line rapidity. I present a preliminary extraction of the CS kernel using the "double ratio", and discuss the methodology employed.

Speaker: Wayne Morris (National Yang Ming Chiao Tung University)

2:40 PM Transverse momentum dependent structure from topological QCD vacuum

We present a general framework originated from topologically nontrivial configurations, known as instantons in the QCD vacuum, to evaluate the non-perturbative transverse partonic structure of hadrons. Within this approach, we derive the transverse-momentum-dependent parton distribution functions (TMDPDFs) for the pion, kaon, and rho meson, as well as the Collins–Soper (CS) kernel that governs their rapidity evolution. Our results provide a tomographic view of the pion and kaon in both parton momentum fraction $x$ and transverse coordinate space $b_T$. The extracted CS kernel, when combined with perturbative contributions, shows good agreement with recent lattice QCD results and phenomenological fits. Notably, we find that the CS kernel exhibits logarithmic growth at large quark transverse separation, offering an important constraint for its phenomenological parametrization. Lastly, our framework allows direct comparison with lattice calculations in Euclidean signature, providing a novel method to evaluate the soft function and extract the CS kernel via analytic continuation.

Speaker: Wei-Yang Liu (Stony Brook University)

3:05 PM Gauge-invariant nonperturbative renormalization of HQET-like operators in Lattice-QCD

Designing good schemes to connect bare operators used in Lattice-QCD to perturbatively defined schemes (such as MSbar) is crucial for Lattice-QCD calculations. Operators containing Wilson Lines (for example those required for a quasi-pdf) contain an additional power divergence in the length of the Wilson Line. In this talk, I'll introduce gauge invariant position-space renormalization schemes that do not require separate renormalization conditions for this power divergence.

Speaker: Joshua Lin (Argonne National Laboratory)

3:30 PM → 4:00 PM Coffee Break

4:00 PM → 5:30 PM Discussion

Fri, October 10

9:00 AM → 10:30 AM Session VII

9:00 AM Heavy meson light-cone distribution amplitudes from lattice QCD

Heavy meson light-cone distribution amplitudes (LCDAs) are essential nonperturbative quantities that characterize the internal dynamics of heavy mesons. They play a crucial role in the theoretical description of heavy meson (B or D) exclusive decays. However, due to the intrinsic challenges of nonperturbative QCD, first-principles calculations of heavy meson LCDAs have been notoriously difficult, with most studies relying on phenomenological models. We proposed a sequential effective theory approach to compute heavy meson LCDAs from first principles using lattice QCD. In this talk, we will present our latest results for heavy meson LCDAs obtained from lattice QCD calculations extrapolated to the continuum limit.

Speaker: Xue-Ying Han (IHEP)

9:25 AM The x-dependent LCDAs: from Mesons to Baryons

The lattice QCD computation of parton distributions within the framework of large momentum effective theory (LaMET) constitutes a first-principles approach to studying hadron structures. Building upon preceding studies on meson systems, we have developed and partly implemented lattice methodologies for calculating the leading twist LCDAs of light baryons under the LaMET formalism over the past few years. In this talk, we will introduce our series of works on the ab initio determination of leading-twist LCDAs of light baryons and present preliminary numerical results. We will discuss the complexities involved in lattice calculations of baryonic systems compared to mesonic systems and report some techniques developed and employed recently to achieve physical results for the more intricate baryonic systems, including special operator selections, the hybrid renormalization scheme, and Fourier inversion strategies.

Speaker: Haoyang Bai (Institute of High Energy Physics, CAS)

9:50 AM x-dependent Light Baryon LCDAs from Lattice QCD

We present the results of lattice QCD calculation of all leading-twist x-dependent Light-cone Distribution Amplitudes (LCDAs) for baryons in light octet, within the framework of Large-momentum Effective Theory (LaMET). We implement a novel Hybrid renormalization scheme for baryon nonlocal operators, and perform simulations at 4 different lattice spacings a = {0.052, 0.068, 0.077, 0.105} fm, achieving reliable and precise results of x-dependent baryon LCDAs. To access the large momentum regime and facilitate matching to light-cone, we simulate the quasi-Distribution Amplitudes (quasi-DAs) with hadron momenta Pz of about 1~3 GeV. The numerical calculations employ CLQCD ensembles with stout smeared clover fermions and a Symanzik gauge action, and several new techniques are also developed to improve the extrapolation and inversion in matching procedure. We present the resulting momentum-fraction distributions for the two light quarks in the light baryon.

Speaker: Mu-Hua Zhang (Shanghai Jiao Tong University)

10:10 AM LCDA Moments of Mesons from Local and Non-local Operators

We determine the leading-twist light-cone distribution amplitude (LCDA) moments of mesons on MILC ensembles using the HYP-smeared clover action, employing both twist-2 local operators and quasi-DA correlators. Based on the twist-2 local operator, we obtain highly precise values for the meson LCDA moments at the physical point and in the continuum limit. By comparing the results from these two methods, we conclude that higher-twist contributions can be effectively suppressed at large momenta, and that the current deviations are mainly due to excited-state contamination. Furthermore, we have identified a computational scheme that can significantly suppress excited-state contamination.

Speaker: Ji-Hao Wang (Institute of Theoretical Physics，Chinese Academy of Sciences)

10:30 AM → 11:00 AM Coffee Break

11:00 AM → 12:40 PM Session VIII

11:00 AM Calculation of the fourth Mellin moment of the pion distribution amplitude using the HOPE method

The pion light-cone distribution amplitude (LCDA) is an essential non-perturbative input for a range of high-energy exclusive processes in quantum chromodynamics. Building upon previous work, I will describe the calculation of the fourth Mellin moment of the pion LCDA in the continuum using the heavy-quark operator product expansion (HOPE) method.

Speaker: Robert Perry (Massachusetts Institute of Technology)

11:25 AM PDFs from four-point functions on the lattice

Among other approaches developed in recent years, four-point functions provide access to the $x$ dependence of parton distribution functions (PDFs). One of the corresponding methods is often referred to as the lattice cross section (LCS) approach: in this method, hadronic matrix elements of two local quark-bilinears located at equal time are factorized in terms of a PDF and a perturbative matching kernel by employing the operator product expansion (OPE). The corresponding matrix elements can be obtained by evaluating four-point functions on the lattice. The method has several advantages, for instance the renormalization of the local operators is comparably straightforward. In this talk, I will present some of my recent and ongoing work for nucleon PDFs using the clover fermion ensembles generated by the CLS collaboration.

Speaker: Christian Zimmermann (Lawrence Berkeley National Laboratory)

11:50 AM Parton Distributions on a Quantum Computer

We perform the first quantum computation of parton distribution function (PDF) with a real quantum device by calculating the PDF of the lightest positronium in the Schwinger model with IBM quantum computers. The calculation uses 10 qubits for staggered fermions at five spatial sites and one ancillary qubit. The most critical and challenging step is to reduce the number of two-qubit gate depths to around 500 so that sensible results start to emerge. The resulting lightcone correlators have excellent agreement with the classical simulator result in central values, although the error is still large. Compared with classical approaches, quantum computation has the advantage of not being limited in the accessible range of parton momentum fraction x due to renormalon ambiguity, and the difficulty of accessing non-valence partons. A PDF calculation with 3+1 dimensional QCD near x=0 or x=1 will be a clear demonstration of the quantum advantage on a problem with great scientific impact.

Speaker: Jiunn-Wei Chen (National Taiwan University)

12:15 PM Lattice Determination of Parton Distributions Through Neural Network

We propose a framework for the reconstruction of parton distribution functions (PDFs) and generalized parton distributions (GPDs) from lattice QCD, utilizing artificial neural networks (ANNs). Our approach combines two complementary methodologies: the Large Momentum Effective Theory (LaMET) and the short-distance operator expansion (SDE). To determine ANN-based PDFs and GPDs, we achieve a joint reconstruction that incorporates quasi-matrix elements from LaMET and matched Ioffe-time distributions derived from SDE. Our framework successfully recovers PDFs and GPDs from mock data and is applied for actual lattice QCD data. It mitigates the individual limitations inherent in LaMET and SDE, while leveraging the ANN architecture to enable a robust reconstruction.

Speaker: Min-Huan Chu (Adam Mickiewicz University)