Effective field theory for radiative corrections to charged-current processes II: Axial-vector coupling

TL;DR

This paper develops a theoretical framework to accurately compute radiative corrections to the axial-vector coupling in weak processes, facilitating precise comparisons between experimental and lattice QCD results to probe new physics.

Contribution

It introduces a matching of the Standard Model to chiral perturbation theory for radiative corrections to $g_A$, including strategies for non-perturbative input determination.

Findings

Representation of corrections in terms of convolutions with nucleon matrix elements

Discussion of data, lattice-QCD, and hadronic model inputs

Enabling precise $g_A/g_V$ ratio comparisons for new physics constraints

Abstract

We discuss the hadronic structure-dependent radiative corrections to the axial-vector coupling that controls single-nucleon weak charged-current processes -- commonly denoted by $g_A$. We match the Standard Model at the GeV scale onto chiral perturbation theory at next-to-leading order in the one-nucleon sector, in the presence of electromagnetic and weak interactions. As a result, we provide a representation for the corrections to $g_A$ in terms of infrared finite convolutions of simple kernels with the single-nucleon matrix elements of time-ordered products of two and three quark bilinears (vector, axial-vector, and pseudoscalar). We discuss strategies to determine the required non-perturbative input from data, lattice-QCD (+QED), and possibly hadronic models. This work paves the way for a precise comparison of the values of the ratio $g_A/g_V$ extracted from experiment and from lattice-QCD, which constrain physics beyond the Standard Model.