Unpolarized gluon distribution in the nucleon from lattice quantum chromodynamics

TL;DR

This paper presents a first-principles lattice QCD calculation of the unpolarized gluon distribution in the nucleon, providing new insights into gluon structure from fundamental theory.

Contribution

The study introduces a novel lattice QCD approach to determine the unpolarized gluon distribution directly from first principles, including advanced techniques like distillation and gradient flow.

Findings

First lattice QCD determination of gluon Ioffe-time distribution.

Calculated gluon distribution at $\,ar{MS}$ scheme, $\, ext{μ} = 2$ GeV.

Results are consistent with phenomenological models.

Abstract

In this study, we present a determination of the unpolarized gluon Ioffe-time distribution in the nucleon from a first principles lattice quantum chromodynamics calculation. We carry out the lattice calculation on a $32^3\times 64$ ensemble with a pion mass of $358$ MeV and lattice spacing of $0.094$ fm. We construct the nucleon interpolating fields using the distillation technique, flow the gauge fields using the gradient flow, and solve the summed generalized eigenvalue problem to determine the glounic matrix elements. Combining these techniques allows us to provide a statistically well-controlled Ioffe-time distribution and unpolarized gluon PDF. We obtain the flow time independent reduced Ioffe-time pseudo-distribution, and calculate the light-cone Ioffe-time distribution and unpolarized gluon distribution function in the $\overline{\rm MS}$ scheme at $\mu = 2$ GeV, neglecting the mixing of the gluon operator with the quark singlet sector. Finally, we compare our results to phenomenological determinations.