Lattice-QCD determination of the hyperon axial couplings in the continuum limit

Abstract

We present the first chiral-continuum--finite-volume extrapolation of the hyperon octet axial couplings (${g}_{\mathrm{\ensuremath{\Sigma}}\mathrm{\ensuremath{\Sigma}}}$ and ${g}_{\mathrm{\ensuremath{\Xi}}\mathrm{\ensuremath{\Xi}}}$) from ${N}_{f}=2+1+1$ lattice QCD. These couplings are important parameters in the low-energy effective field theory description of the octet baryons and are fundamental to the nonleptonic decays of hyperons and to hyperon-hyperon and hyperon-nucleon scattering with applications to neutron stars. We use clover lattice fermion action for the valence quarks with sea quarks coming from configurations of ${N}_{f}=2+1+1$ highly improved staggered quarks generated by MILC Collaboration. Our work includes the first calculation of ${g}_{\mathrm{\ensuremath{\Sigma}}\mathrm{\ensuremath{\Sigma}}}$ and ${g}_{\mathrm{\ensuremath{\Xi}}\mathrm{\ensuremath{\Xi}}}$ directly at the physical pion mass on the lattice, and a full account of systematic uncertainty, including excited-state contamination, finite-volume effects, and continuum extrapolation, all addressed for the first time. We find the ratio of the continuum-limit hyperon coupling constants with respect to the nucleon axial charges to be ${g}_{\mathrm{\ensuremath{\Sigma}}\mathrm{\ensuremath{\Sigma}}}/{g}_{A}=0.351(6)(2)$ and ${g}_{\mathrm{\ensuremath{\Xi}}\mathrm{\ensuremath{\Xi}}}/{g}_{A}=\ensuremath{-}0.213(5)(1)$, where the first error includes the statistical and extrapolation systematic uncertainties, and the second error corresponds to systematics associated with varying lattice parameters. The SU(3) symmetry breaking derived from these axial charges is 9%, which is about a factor of 2 smaller than earlier lattice estimates.