Recent Progress in Lattice Parton-Distribution Calculations

TL;DR

This paper reviews recent lattice-QCD calculations of parton distribution functions using the LaMET framework, highlighting new results on nucleon, strange, charm, pion, and kaon PDFs, and comparing GPDs with traditional methods.

Contribution

It presents new lattice-QCD results on various parton distributions and GPDs at physical pion mass, utilizing improved fermion actions and multiple lattice spacings, advancing the understanding of hadron structure.

Findings

First continuum-physical isovector nucleon PDF from lattice-QCD.

Initial results on strange and charm PDFs.

Analysis of GPDs' $Q^2$ and $x$ dependence at physical pion mass.

Abstract

The large-momentum effective theory (LaMET) framework has been widely used to determine the Bjorken-$x$ dependence of parton distribution functions (PDFs) in lattice-QCD hadron-structure calculations. In this proceeding, I highlighted selected recent lattice-QCD results on parton distributions from MSULat group. We use clover valence fermions on ensembles generated by MILC Collaboration with lattice spacing $a \approx 0.06$, 0.09, and 0.12 fm, with $M_\pi L \approx 4$, and with pion masses including 135, 220 and 310 MeV and $N_f=2+1+1$ flavors of highly improved staggered dynamical quarks. Results include the continuum-physical isovector nucleon PDF, a first study of the strange and charm PDFs and the pion and kaon valence-quark PDFs. We also reported results on the $Q^2$ and $x$ dependence of nucleon isovector unpolarized and helicity GPDs calculated directly at physical pion mass; we also make a comparison of the GPDs with the traditional moment methods from other lattice calculations.