Axial coupling constant of the nucleon for two flavours of dynamical quarks in finite and infinite volume

TL;DR

This study computes the nucleon axial coupling constant g_A using lattice QCD with two dynamical quark flavors, applying a novel chiral and volume extrapolation method to reach the physical and infinite volume limits.

Contribution

It introduces a combined finite volume and chiral extrapolation formula for g_A based on chiral effective field theory, improving the accuracy of lattice QCD predictions.

Findings

Determined g_A in the chiral limit without fixing to the physical value.

Provided a non-perturbative renormalization of g_A.

Demonstrated the effectiveness of the extrapolation formula in lattice QCD.

Abstract

We present data for the axial coupling constant g_A of the nucleon obtained in lattice QCD with two degenerate flavours of dynamical non-perturbatively improved Wilson quarks. The renormalisation is also performed non-perturbatively. For the analysis we give a chiral extrapolation formula for g_A based on the small scale expansion scheme of chiral effective field theory for two degenerate quark flavours. Applying this formalism in a finite volume we derive a formula that allows us to extrapolate our data simultaneously to the infinite volume and to the chiral limit. Using the additional lattice data in finite volume we are able to determine the axial coupling of the nucleon in the chiral limit without imposing the known value at the physical point.