Nucleon charges and quark momentum fraction with $N_f=2+1$ Wilson fermions

TL;DR

This study calculates nucleon charges and quark momentum fractions using $N_f=2+1$ Wilson fermions on multiple lattice ensembles, carefully controlling excited-state contamination and performing chiral, continuum, and finite size extrapolations.

Contribution

It provides a comprehensive analysis of nucleon structure with multiple lattice spacings and pion masses, including excited-state effects and extrapolations, advancing previous lattice QCD studies.

Findings

Results include isovector charges and twist-2 matrix elements.

Systematic control of excited-state contamination through multiple source-sink separations.

Physical results obtained after chiral, continuum, and finite size extrapolations.

Abstract

We present a nucleon structure analysis including local isovector charges as well as twist-2 operator insertions. Computations are performed on CLS ensembles with $N_f=2+1$ Wilson fermions, covering four values of the lattice spacing and pion masses down to $M_\pi \approx 200\,\mathrm{MeV}$. Several source-sink separations (typically $\sim 1.0\,\mathrm{fm}$ to $\sim 1.5\,\mathrm{fm}$) allow us to assess excited-state contaminations. Results on each ensemble are obtained from simultaneous two-state fits including all observables and all available source-sink separations with the mass gap as a free fit parameter. Finally, the chiral, continuum and finite size extrapolation is performed to extract physical results.