The isovector axial form factor of the nucleon from lattice QCD

TL;DR

This paper presents a lattice QCD calculation of the nucleon's isovector axial form factor, introducing a new extraction method and providing a parametrization that aligns with previous lattice results but differs from scattering data.

Contribution

A novel method to directly extract the axial form factor's z-expansion from lattice correlators is introduced, enhancing the precision of form factor parametrization.

Findings

Form factor parametrization extends up to 0.7 GeV^2 with quantified uncertainties.

Results agree with previous lattice calculations.

Form factor is less steep than neutrino-deuterium scattering data suggests.

Abstract

The isovector axial form factor of the nucleon plays a key role in interpreting data from long-baseline neutrino oscillation experiments. We perform a lattice-QCD based calculation of this form factor, introducing a new method to directly extract its $z$-expansion from lattice correlators. Our final parametrization of the form factor, which extends up to spacelike virtualities of $0.7\,{\rm GeV}^2$ with fully quantified uncertainties, agrees with previous lattice calculations but is significantly less steep than neutrino-deuterium scattering data suggests.