Quark flavor decomposition of the nucleon axial form factors

TL;DR

This paper computes the flavor decomposition of nucleon axial form factors, including disconnected contributions and strange/charm quark effects, using lattice QCD with physical quark masses, revealing SU(3) symmetry breaking and meson coupling insights.

Contribution

It provides the first comprehensive flavor decomposition of nucleon axial form factors including disconnected contributions and strange/charm quark effects using physical quark mass simulations.

Findings

Up to 10% SU(3) flavor symmetry breaking for axial form factors.

Up to 50% breaking for induced pseudoscalar form factors.

Determined the pseudoscalar coupling g_{ηNN} and Goldberger-Treiman discrepancy.

Abstract

We present results on the isoscalar form factors including the disconnected contributions, as well as on the strange and charm quark form factors. Using previous results on the isovector form factors, we determine the flavor decomposition of the nucleon axial form factors. These are computed using an ensemble of $N_f=2+1+1$ twisted mass fermions simulated with physical values of quark masses. We investigate the SU(3) flavor symmetry and show that there is up to 10\% breaking for the axial and up to 50\% for the induced pseudoscalar form factors. By fitting the $Q^2$-dependence, we determined the corresponding root mean square radii. The pseudoscalar coupling of the $\eta$ meson and the nucleon is found to be $g_{\eta NN}=3.7(1.0)(0.7)$, and the Goldberger-Treiman discrepancy for the octet combination about 50\%.