Improved determination of hadron matrix elements using the variational method

TL;DR

This paper demonstrates that the variational method improves the accuracy and efficiency of extracting hadron matrix elements in lattice QCD by reducing excited state contamination compared to traditional methods.

Contribution

The study applies the variational method to calculate nucleon axial charge gA, showing it outperforms summation and two-exponential fit techniques in robustness and efficiency.

Findings

Variational method reduces excited state contamination.

Results are more consistent across different analyses.

Improved determination of nucleon matrix elements.

Abstract

The extraction of hadron form factors in lattice QCD using the standard two- and three-point correlator functions has its limitations. One of the most commonly studied sources of systematic error is excited state contamination, which occurs when correlators are contaminated with results from higher energy excitations. We apply the variational method to calculate the axial vector current gA and compare the results to the more commonly used summation and two-exponential fit methods. The results demonstrate that the variational approach offers a more efficient and robust method for the determination of nucleon matrix elements.