Nucleon Axial Form Factor from Lattice QCD

TL;DR

This paper presents lattice QCD calculations of the proton's isovector axial form factors, comparing different current types and quark masses, and finds reasonable agreement with experimental data after extrapolation.

Contribution

It provides new lattice QCD results for the axial form factors using both point-split and local currents across various quark masses, including heavy quarks, and determines finite lattice renormalization.

Findings

Axial form factor $q^2$ dependence agrees with experiment after chiral extrapolation.

Calculated axial coupling constants are slightly smaller than experimental values.

Finite lattice renormalization factors are determined for heavy quark currents.

Abstract

Results for the isovector axial form factors of the proton from a lattice QCD calculation are presented for both point-split and local currents. They are obtained on a quenched $16^{3} \times 24$ lattice at $\beta= 6.0$ with Wilson fermions for a range of quark masses from strange to charm. We determine the finite lattice renormalization for both the local and point-split currents of heavy quarks. Results extrapolated to the chiral limit show that the $q^2$ dependence of the axial form factor agrees reasonably well with experiment. The axial coupling constant $g_A$ calculated for the local and the point-split currents is about 6\% and 12\% smaller than the experimental value respectively.