Generalised Parton Distributions from Lattice Feynman-Hellmann Techniques

TL;DR

This paper demonstrates the use of Feynman-Hellmann techniques in lattice QCD to calculate generalized parton distributions, successfully extracting moments including the first determination of the n=4 moments at unphysical pion mass.

Contribution

It introduces a novel application of Feynman-Hellmann methods to compute GPD moments in lattice QCD, including higher moments previously uncalculated.

Findings

First determination of n=4 GPD moments in lattice QCD.

Extraction of GPD moments at two different momentum transfers.

Demonstration of Feynman-Hellmann techniques for off-forward amplitudes.

Abstract

We report on the use of Feynman-Hellmann techniques to calculate the off-forward Compton amplitude (OFCA) in lattice QCD. At leading-twist, the Euclidean OFCA is parameterised by the Mellin moments of generalised parton distributions (GPDs). Hence we extract GPD moments for two values of the soft momentum transfer, $t=-1.10, -2.20\;\text{GeV}^2$ and zero-skewness kinematics at an unphysical pion mass of $m_{\pi}\approx 470\;\text{MeV}$. This includes the first determination of the $n=4$ moments.