Nucleon Tomography and Generalized Parton Distribution at Physical Pion Mass from Lattice QCD

TL;DR

This paper reports the first lattice QCD calculation of the nucleon generalized parton distributions at the physical pion mass, providing new insights into nucleon structure through three-dimensional distributions and impact-parameter tomography.

Contribution

It introduces a novel lattice QCD approach to compute GPDs at physical pion mass with nonperturbative renormalization and momentum smearing, advancing nucleon structure studies.

Findings

First lattice GPD calculation at physical pion mass

Provides 3D distributions and impact-parameter tomography

Results at nonzero momentum transfer in specified range

Abstract

We present the first lattice calculation of the nucleon isovector unpolarized generalized parton distribution (GPD) at the physical pion mass using a lattice ensemble with 2+1+1 flavors of highly improved staggered quarks (HISQ) generated by MILC Collaboration, with lattice spacing $a\approx 0.09$~fm and volume $64^3\times 96$. We use momentum-smeared sources to improve the signal at nucleon boost momentum $P_z \approx 2.2$ GeV, and report results at nonzero momentum transfers in $[0.2,1.0]\text{ GeV}^2$. Nonperturbative renormalization in RI/MOM scheme is used to obtain the quasi-distribution before matching to the lightcone GPDs. The three-dimensional distributions $H(x,Q^2)$ and $E(x,Q^2)$ at $\xi=0$ are presented, along with the three-dimensional nucleon tomography and impact-parameter--dependent distribution for selected Bjorken $x$ at $\mu=3$ GeV in $\overline{\text{MS}}$ scheme.