In this report, an updated result on both quark helicity and unpolarized colinear PDFs are calculated using CLQCD ensembles within the framework of LaMET. This calculation is dedicated to give one of the newest results with continous extrapolation performed on physical point. NNLO Wilsonian coefficients and matching kernels with leading-renormalon resummation and renormalization group...
This report presents a lattice QCD study of parton distribution functions using current-current correlators within LAME. Unlike conventional quasi-PDF approaches based on Wilson-line operators, current-current correlators have simpler renormalization properties and avoid linear power divergences and associated renormalon ambiguities. We formulate the large-momentum expansion for vector-vector...
The proton's unpolarized $u(x)-d(x)$ parton distribution function (PDF) has been studied by a number of lattice QCD groups through large momentum expansion. However, due to lattice artifacts (excited state contaminations, unphysical pion masses, and discretization effects) and less-advanced theoretical analysis (renormalizations, large-distance extrapolations, and large-log resummations), the...
In recent years, the $x$-dependence of parton distribution functions (PDFs) has become accessible through non-local operators of a boosted hadron by utilizing techniques such as large momentum effective theory (LaMET) and short distance factorization (SDF). Embedded in these distribution functions are Mellin moments, which contain information on fundamental properties of hadrons, such as the...
We present the first Coulomb-gauge calculation of the nucleon unpolarized parton distribution functions (PDFs) at the physical pion mass. Both the isovector and connected isoscalar channels are computed within the large-momentum effective theory (LaMET) framework on a $2+1$ flavor ensemble with lattice spacing $a = 0.076$ fm. By employing kinematically enhanced interpolating operators, we...
We report a state-of-the-art lattice QCD calculation of the total gluon helicity contribution to the proton spin, $\Delta G$. After extrapolating to the continuum limit, $\Delta G$ is found to be $\Delta G=0.231(17)^{sta.}(44)^{sym.} at the $\overline{\mathrm{MS}}$ scale $\mu^2=10\ \mathrm{GeV}^2$, which constitutes approximately 46(9)% of the proton spin. In addition, we will also provide a...
Gluon parton distribution functions (PDFs) from large momentum effective theory (LaMET) have remained in poor statistical precision compared to non-singlet PDFs due to their correlators coming solely from disconnected diagrams. One method to improve the long distance signal is to remove the Wilson lines from the correlators, which are present solely to maintain gauge invariance, and compute...
We present a lattice QCD determination of the Mellin moments of the unpolarized gluon parton distribution function in the proton. The analysis is based on matrix elements of nonlocal gluon operators coupled to momentum-boosted proton states. The calculation relies on an $N_f=2+1+1$ ensemble of maximally twisted mass fermions with clover improvement and the Iwasaki-improved gauge action, at a...
Light-cone distribution amplitudes (LCDAs) of heavy hadrons play a central role in the QCD description of exclusive processes involving heavy quarks. They encode essential nonperturbative information and provide key inputs for phenomenological analyses based on factorization. In this talk, I will present recent progress on the structure and determination of heavy-hadron LCDAs, with emphasis on...
We present the first lattice QCD calculation of all components of the leading-twist light-cone distribution amplitudes (LCDAs) of baryons at the physical pion mass and in the continuum limit, within the Large-Momentum Effective Theory (LaMET) framework.
This work provides a systematic first-principles determination of baryon LCDAs beyond moment-based approaches, enabling direct access to...
We determine the leading-twist light-cone distribution amplitude (LCDA) moments of mesons using the HYP-smeared clover action on MILC ensembles, employing both twist-2 local operators and the LaMET approach. From the twist-2 local operators, we obtain high-precision values for the meson LCDA moments at the physical point and in the continuum limit. A comparison between the two methods shows...
I will consider in the effective field theory framework how UV quantum fluctuations destroy the concept of light travel and partons, unless in an asymptotic free theory.
With the future Electron Ion Collider on the horizon, Generalized Parton Distributions (GPDs) have attracted significant interest over the past years. As a tool to map out the three-dimensional structure of hadrons, they offer unique opportunities to study Quantum Chromodynamics (QCD) and complex partonic correlators at non-perturbative scales. However, their experimental extraction is...
We calculate the ``kinematic'' corrections $t/P_z^2$ and $m_N^2/P_z^2$ to the short distance expansion of gauge-invariant nonlocal quark-antiquark operators sandwiched between nucleon states with different momenta. Here $t$ is the momentum transfer, $m_N$ is the nucleon mass and $P_z$ is the momentum component in the direction of the quark-antiquark separation, which is assumed to be...
This talk presents an extraction of Mellin moments of the proton unpolarized generalized parton distributions (GPDs) at nonzero skewness from lattice QCD. The analysis builds on the recent studies of GPDs at nonzero skewness, which, together with the polynomiality relations and short-distance factorization matching, connect the moments to generalized form factors. The present method uses...
Understanding and controlling systematic uncertainties is one of the main challenges in lattice QCD calculations. In this work, we investigate the momentum transfer ($t$) dependence of Mellin moments for unpolarized proton generalized parton distributions (GPDs) at zero skewness. The ground-state matrix elements are extracted using plateau fits and subsequently renormalized using the double...
The transverse-momentum-dependent parton distribution function (TMDPDF) encodes essential information on the three-dimensional momentum structure of hadrons and plays a central role in QCD factorization for semi-inclusive processes. A first-principles determination of TMDPDFs remains highly challenging because of their intrinsically nonperturbative nature and the presence of both ultraviolet...
TMD quantities, such as TMDPDFs, provide essential information on the three-dimensional structure of hadrons and serve as key nonperturbative inputs for high-energy scattering processes, including SIDIS and Drell–Yan production. Unlike collinear PDFs, TMDs involve near-light-cone Wilson lines and therefore suffer from rapidity divergences arising from the separation of soft and collinear...
We present the results of the first lattice calculation of the Collins-Soper (CS) kernel from a vacuum soft function, which is constructed from space-like Wilson lines with complex direction vectors. Employing three ensembles of pure SU(3) gauge configurations at fine lattice spacings, we achieve high statistical precision in computing the soft function, whose rapidity dependence is well...
At large hadron momentum, quasi-transverse-momentum-dependent distributions (quasi-TMDs) defined from Coulomb-gauge correlators can be expanded and perturbatively matched to the light-cone TMDs up to the subtraction of an intrinsic soft function. In this talk, I will discuss the derivation of the operator definition of this soft function, as well as the method to extract it from a meson form...
We present a lattice quantum chromodynamics (QCD) calculation of the proton valence-quark transverse-momentum-dependent parton distribution function (TMDPDF) in three polarization channels within the framework of large-momentum effective theory (LaMET). Using correlators fixed in the Coulomb gauge (CG), we computed the quasi-TMD beam function for a proton with the chiral-symmetry-preserving...
The recent proposal to use nonlocal, Coulomb gauge-fixed operators in a LaMET framework to measure hadron structure properties has seen great success, as it circumvents poor signal-to-noise issues present with Wilson line operators. In this contribution, I will discuss nonperturbative renormalization schemes for Coulomb gauge-fixed operators, including RI'-MOM schemes adapted to only use...
The instanton liquid model is believed to capture the main features of vacuum QCD dynamics. Recently, multiple predictions for hadron structure functions have been derived and compared with experimental measurements and lattice QCD calculations, showing general agreement. In order to explore the precision of the instanton liquid model, one has to compare its predictions with non-perturbative...
Partons provide a natural language for hadron structure at high energies in QCD. However, direct light-front (LF) quantization leads to severe infrared singularities. These divergences reflect the absence of an intrinsic IR scale and nontrivial vacuum structure, thus placing QCD at a critical point. As a result, well-defined parton distributions are constructed through renormalization prior to...
The light-cone distribution amplitude (LCDA) is a non-perturbative quantity for understanding hadron structure and exclusive scattering processes. We present on our calculation of moments of the pion and kaon LCDAs using the heavy-quark operator product expansion (HOPE) framework. This method employs an OPE analysis of hadronic amplitudes through the inclusion of a fictitious valence heavy...
Calculating parton functions from first principles remains a major challenge: they require matrix elements with a Wilson line along a light-like direction, which are not directly accessible in the Euclidean lattice formulation underlying conventional Monte Carlo simulations. In contrast, the Hamiltonian formalism allows for a direct treatment of light-cone dynamics, complementing indirect...
I will describe our attempts to compute the meson lightcone distribution amplitude and a meson GPD on a quantum computer.
