Moments of nucleon generalized parton distributions from lattice QCD

TL;DR

This study computes the lower moments of nucleon generalized parton distributions using lattice QCD with multiple lattice spacings and volumes, providing insights into quark spin contributions in the nucleon.

Contribution

It presents non-perturbatively renormalized lattice QCD results for nucleon GPD moments across different lattice parameters, including chiral extrapolation to the physical point.

Findings

Results are given in the MS-bar scheme at 2 GeV.

Investigation of cut-off effects and volume dependence.

Implications for quark spin contribution to the nucleon.

Abstract

We present results on the lower moments of the nucleon generalized parton distri butions within lattice QCD using two dynamical flavors of degenerate twisted mass fermions. Our simulations are performed on lattices with three different values of the lattice spacings, namely $a=0.089$ fm, $a=0.070$ fm and $a=0.056$ fm, allowing the investigation of cut-off effects. The volume dependence is examined using simulations on two lattices of spatial length $L=2.1$ fm and $L=2.8$ fm. The simulations span pion masses in the range of 260-470 MeV. Our results are renormalized non-perturbatively and the values are given in the $\bar{\rm MS}$ scheme at a scale $ \mu=2$ GeV. They are chirally extrapolated to the physical point in order to compare with experiment. The consequences of these results on the spin carried by the quarks in the nucleon are investigated.