The nucleon axial charge from lattice QCD with controlled errors

TL;DR

This paper presents a lattice QCD calculation of the nucleon axial charge gA, carefully controlling systematic errors and excited state contamination, resulting in a value consistent with experimental measurements.

Contribution

The study introduces a method using summed operator insertions to better control excited state contamination in lattice QCD calculations of gA.

Findings

Calculated gA = 1.223 with combined errors.

Controlled systematic errors and excited state effects.

Results agree with experimental values.

Abstract

We report on our calculation of the nucleon axial charge gA in QCD with two flavours of dynamical quarks. A detailed investigation of systematic errors is performed, with a particular focus on contributions from excited states to three-point correlation functions. The use of summed operator insertions allows for a much better control over such contamination. After performing a chiral extrapolation to the physical pion mass, we find gA=1.223 +/- 0.063 (stat) +0.035 -0.060 (syst), in good agreement with the experimental value.