Chiral extrapolation of lattice moments of proton quark distributions

TL;DR

This paper resolves a long-standing discrepancy between lattice QCD calculations and experimental measurements of proton quark distribution moments by introducing a chiral extrapolation formula that incorporates QCD's chiral symmetry constraints.

Contribution

It proposes a simple, symmetry-based extrapolation formula for lattice moments that accurately matches both lattice data and experimental results.

Findings

Excellent agreement between extrapolated lattice moments and experimental data

Inclusion of nonanalytic behavior improves the extrapolation accuracy

Addresses previous discrepancies in lattice QCD calculations of proton structure

Abstract

We present the resolution of a long-standing discrepancy between the moments of parton distributions calculated from lattice QCD and their experimental values. We propose a simple extrapolation formula for the moments of the nonsinglet quark distribution u-d, as a function of quark mass, which embodies the general constraints imposed by the chiral symmetry of QCD. The inclusion of the leading nonanalytic behavior leads to an excellent description of both the lattice data and the experimental values of the moments.