Nucleon axial coupling from Lattice QCD

TL;DR

This paper reports a high-precision lattice QCD calculation of the nucleon axial coupling, demonstrating improved methods and control over uncertainties, resulting in a value close to experimental measurements.

Contribution

The study introduces an improved Feynman-Hellmann inspired method for calculating three-point functions in lattice QCD, enhancing signal quality and systematic control.

Findings

Preliminary value of g_A = 1.285(17) with 1.33% uncertainty

Performed calculations at multiple pion masses, lattice spacings, and volumes

Demonstrated control over systematic uncertainties in the lattice QCD calculation

Abstract

We present state-of-the-art results from a lattice QCD calculation of the nucleon axial coupling, $g_A$, using M\"obius Domain-Wall fermions solved on the dynamical $N_f = 2 + 1 + 1$ HISQ ensembles after they are smeared using the gradient-flow algorithm. Relevant three-point correlation functions are calculated using a method inspired by the Feynman-Hellmann theorem, and demonstrate significant improvement in signal for fixed stochastic samples. The calculation is performed at five pion masses of $m_\pi\sim \{400, 350, 310, 220, 130\}$~MeV, three lattice spacings of $a\sim\{0.15, 0.12, 0.09\}$~fm, and we do a dedicated volume study with $m_\pi L\sim\{3.22, 4.29, 5.36\}$. Control over all relevant sources of systematic uncertainty are demonstrated and quantified. We achieve a preliminary value of $g_A = 1.285(17)$, with a relative uncertainty of 1.33\%.