Accessing the Gluon Momentum Fraction of Nucleons through the Gradient Flow

TL;DR

This paper presents a lattice QCD calculation of the gluon momentum fraction in nucleons using the gradient flow, nonperturbative renormalization, and advanced analysis techniques to achieve a precise result.

Contribution

It introduces a novel combination of gradient flow, variational method, distillation, and Bayesian averaging to accurately compute the gluon momentum fraction in nucleons.

Findings

Gluon momentum fraction in nucleons is 0.482(35) at 2 GeV.

Employs nonperturbative renormalization with gradient flow.

Reduces systematic uncertainties with advanced analysis methods.

Abstract

We calculate the gluon momentum fraction of the nucleon using lattice quantum chromodynamics (QCD), with a nonperturbative renormalization technique based on the gradient flow. The gluon momentum fraction is determined on a single Wilson-clover ensemble using Nf = 2+1 flavors with pion mass 358 MeV and lattice spacing 0.094 fm. We employ the variational method to reduce excited-state contamination and apply the distillation framework to ensure a large operator basis. To reduce systematic uncertainties, we apply Bayesian model averaging to all fit procedures. We apply matching coefficients to the flow-time dependent lattice results to recover the gluon momentum fraction in the MS-scheme at 2 GeV. Our final result is <x>_g(\mu = 2 GeV) = 0.482(35), where we quote only statistical uncertainties.