Moments of Isovector Quark Distributions from Lattice QCD

TL;DR

This paper analyzes lattice QCD calculations of isovector quark distribution moments, focusing on chiral extrapolation and loop corrections, revealing different behaviors for polarized and unpolarized moments.

Contribution

It provides a comprehensive chiral extrapolation of lattice moments including N pi and Delta pi loop corrections, highlighting their impact on polarized versus unpolarized moments.

Findings

Unpolarized moments show significant curvature near the chiral limit.

Polarized moments remain nearly linear, with minimal deviation.

Loop corrections partially cancel, affecting the moments differently.

Abstract

We present a complete analysis of the chiral extrapolation of lattice moments of all twist-2 isovector quark distributions, including corrections from N pi and Delta pi loops. Even though the Delta resonance formally gives rise to higher order non-analytic structure, the coefficients of the higher order terms for the helicity and transversity moments are large and cancel much of the curvature generated by the wave function renormalization. The net effect is that, whereas the unpolarized moments exhibit considerable curvature, the polarized moments show little deviation from linearity as the chiral limit is approached.