Moments of Nucleon Generalized Parton Distributions in Lattice QCD

TL;DR

This paper introduces a novel lattice QCD technique to accurately compute moments of nucleon generalized parton distributions, significantly improving statistical constraints and enabling precise measurements of form factors and quark angular momentum.

Contribution

A new method exploiting full lattice information to measure generalized form factors with higher accuracy than traditional approaches.

Findings

Reliable signals for n=2 flavor singlet form factors up to 3 GeV^2

Connected diagrams contribute about 1% to total quark angular momentum

Method outperforms conventional techniques in unquenched QCD simulations

Abstract

Calculation of moments of generalized parton distributions in lattice QCD requires more powerful techniques than those previously used to calculate moments of structure functions. Hence, we present a novel approach that exploits the full information content from a given lattice configuration by measuring an overdetermined set of lattice observables to provide maximal statistical constraints on the generalized form factors at a given virtuality, t. In an exploratory investigation using unquenched QCD configurations at intermediate sea quark masses, we demonstrate that our new technique is superior to conventional methods and leads to reliable numerical signals for the n=2 flavor singlet generalized form factors up to 3 GeV^2. The contribution from connected diagrams in the flavor singlet sector to the total quark angular momentum is measured to an accuracy of the order of one percent.