First Lattice QCD Study of Proton Twist-3 GPDs

TL;DR

This paper reports the first lattice QCD calculations of proton twist-3 generalized parton distributions (GPDs) using the quasi-distribution method and Large Momentum Effective Theory, providing new insights into nucleon structure.

Contribution

It introduces a novel lattice QCD approach to compute twist-3 GPDs of the proton using quasi-distributions and LaMET, with calculations at multiple momenta and momentum transfer values.

Findings

First lattice QCD results for twist-3 GPDs

Use of three different momentum boosts

Calculations performed at multiple momentum transfer values

Abstract

We present first results on selected twist-3 quark GPDs using the quasi-distribution method. This approach relates lattice QCD data and light-cone distribution functions using Large Momentum Effective Theory (LaMET). We calculate quark-antiquark correlators of boosted nucleons coupled to non-local operators with vector and axial Dirac structure, which is transverse to the momentum boost. We use three values of the momentum boost, namely 0.83, 1.25, 1.67 GeV. The GPDs are defined in the symmetric (Breit) frame, which we implement here with 4-vector momentum transfer squared of 0, 0.69 and 1.39 GeV 2 , all at zero skewness. The calculation is performed using one ensemble of two degenerate light, a strange and a charm quark ($N_f$ = 2 + 1 + 1) of maximally twisted mass fermions with a clover term, corresponding to a pion mass of 260 MeV.