Variational Approach to the Calculation of gA

TL;DR

This paper uses a variational approach in lattice QCD to accurately compute the nucleon axial charge gA, demonstrating rapid ground state dominance and highlighting the importance of source tuning to avoid excited state contamination.

Contribution

It introduces a variational method for calculating gA in lattice QCD and compares its effectiveness to traditional techniques, emphasizing improved ground state extraction.

Findings

Ground state dominance occurs rapidly in the variational approach.

Excited state effects can cause up to 8% suppression of gA.

Proper source tuning is crucial for accurate gA calculation.

Abstract

We present a lattice QCD calculation of the nucleon axial charge, gA, using a variational approach. After a brief outline of how the variational method is applied to the calculation of form factors, we present results for gA using this method. We find that ground state dominance is rapid, evident in the early onset of a clear plateau in the correlation function ratio proportional to gA. Through a comparison with results obtained via traditional methods, we show how excited state effects can suppress gA by as much as 8% if sources are not properly tuned.