Chiral extrapolation of g_A with explicit Delta(1232) degrees of freedom

TL;DR

This paper analyzes the dependence of the nucleon's axial coupling g_A on quark mass using chiral effective field theory with explicit Delta(1232) degrees of freedom, successfully bridging lattice QCD results and physical values.

Contribution

It demonstrates that including the Delta(1232) explicitly in chiral EFT improves the extrapolation of g_A from lattice data to the physical point, unlike standard chiral perturbation theory.

Findings

Chiral EFT with Delta(1232) matches lattice data effectively.

Standard chiral perturbation theory fails at order p^4 for this extrapolation.

Explicit Delta(1232) inclusion reduces uncontrolled errors for pion masses below 300 MeV.

Abstract

An updated and extended analysis of the quark mass dependence of the nucleon's axial vector coupling constant g_A is presented in comparison with state-of-the-art lattice QCD results. Special emphasis is placed on the role of the Delta(1232) isobar. It is pointed out that standard chiral perturbation theory of the pion-nucleon system at order p^4 fails to provide an interpolation between the lattice data and the physical point. In constrast, a version of chiral effective field theory with explicit inclusion of the Delta(1232) proves to be successful. Detailed error analysis and convergence tests are performed. Integrating out the Delta(1232) as an explicit degree of freedom introduces uncontrolled errors for pion masses m_pi >~ 300 MeV.