Investigation of the Second Moment of the Nucleon's g1 and g2 Structure Functions in Two-Flavor Lattice QCD

TL;DR

This paper calculates the second moments of the nucleon's g1 and g2 structure functions using two-flavor lattice QCD, providing numerical estimates for proton and neutron targets at a specific energy scale.

Contribution

It presents the first lattice QCD computation of the reduced matrix elements a_2 and d_2 for nucleons with dynamical light quarks, including statistical error estimates.

Findings

d_2^(p)=0.004(5) at Q^2=5 GeV^2

d_2^(n)=-0.001(3) at Q^2=5 GeV^2

a_2^(p)=0.077(12) at Q^2=5 GeV^2

Abstract

The reduced matrix elements a_2 and d_2 are computed in lattice QCD with N_f=2 flavors of light dynamical (sea) quarks. For proton and neutron targets we obtain as our best estimates d_2^(p)=0.004(5) and d_2^(n)=-0.001(3), respectively, in the MSbar scheme at Q^2=5 GeV^2, while for a_2 we find a_2^(p)=0.077(12) and a_2^(n)=-0.005(5), where the errors are purely statistical.