Octet baryon isovector charges from $N_f = 2 + 1$ lattice QCD

TL;DR

This paper calculates the isovector charges of various baryons and the up-down quark mass difference using lattice QCD with multiple ensembles, providing results close to physical conditions and analyzing SU(3) flavor symmetry breaking.

Contribution

It presents a comprehensive lattice QCD study of baryon isovector charges and quark mass differences with controlled extrapolations to physical parameters.

Findings

Moderate SU(3) flavor symmetry breaking for axial charges.

No significant symmetry breaking for scalar and tensor charges.

Results are consistent with experimental and theoretical expectations.

Abstract

We determine the axial, scalar and tensor isovector charges of the nucleon, sigma and cascade baryons as well as the difference between the up and down quark masses, $m_u-m_d$. We employ gauge ensembles with $N_f=2+1$ non-perturbatively improved Wilson fermions at six values of the lattice spacing in the range $a\approx (0.039 - 0.098) \,$fm, generated by the Coordinated Lattice Simulations (CLS) effort. The pion mass $M_\pi$ ranges from around $430 \, $MeV down to a near physical value of $130 \, $MeV and the linear spatial lattice extent $L$ varies from $6.5\,M_{\pi}^{-1}$ to $3.0\,M_{\pi}^{-1}$, where $L M_\pi \geq 4$ for the majority of the ensembles. This allows us to perform a controlled interpolation/extrapolation of the charges to the physical mass point in the infinite volume and continuum limit. Investigating SU(3) flavour symmetry, we find moderate symmetry breaking effects for the axial charges at the physical quark mass point, while no significant effects are found for the other charges within current uncertainties.