First moments of the nucleon generalized parton distributions from lattice QCD

TL;DR

This work develops a lattice QCD framework to compute the first moments of nucleon GPDs ($H$ and $E$) by evaluating the generalized form factors $A_{20}$, $B_{20}$, and $C_2$ in $N_f=2$ ensembles. It achieves results at pion masses down to ~260 MeV and performs a one-loop covariant baryon chiral perturbation theory fit to describe the mass dependence. The methodology relies on local twist-two operators and ratios of two- and three-point functions with the sequential-source technique to extract the generalized form factors. Overall, the study provides first-principles insights into the nucleon's spin and spatial-momentum structure by linking lattice QCD results with chiral EFT.

Abstract

We report on our lattice calculations of the nucleon's generalized parton distributions (GPDs), concentrating on their first moments for the case of N_f=2. Due to recent progress on the numerical side we are able to present results for the generalized form factors at pion masses as low as 260 MeV. We perform a fit to one-loop covariant baryon chiral perturbation theory with encouraging results.