Isovector and flavor-diagonal charges of the nucleon

TL;DR

This paper updates calculations of nucleon isovector and flavor-diagonal charges using lattice QCD with multiple ensembles, controlling excited-state contamination and including disconnected diagrams for flavor-diagonal charges.

Contribution

It provides the latest lattice QCD results for nucleon charges with improved control over systematic uncertainties and includes disconnected diagram calculations for flavor-diagonal charges.

Findings

Updated nucleon charge values with reduced uncertainties.

Controlled excited-state contamination through multi-state fits.

Included disconnected diagrams for flavor-diagonal charges.

Abstract

We present an update on the status of the calculations of isovector and flavor-diagonal charges of the nucleon. The calculations of the isovector charges are being done using ten $2+1+1$-flavor HISQ ensembles generated by the MILC collaboration covering the range of lattice spacings $a \approx$ 0.12, 0.09, 0.06 fm and pion masses $M_\pi \approx$ 310, 220, 130 MeV. Excited-states contamination is controlled by using four-state fits to two-point correlators and three-states fits to the three-point correlators. The calculations of the disconnected diagrams needed to estimate flavor-diagonal charges are being done on a subset of six ensembles using the stocastic method. Final results are obtained using a simultaneous fit in $M_\pi^2$, the lattice spacing $a$ and the finite volume parameter $M_\pi L$ keeping only the leading order corrections.