Gluon PDF for the proton using the twisted mass formulation of lattice QCD

TL;DR

This paper computes the gluon parton distribution function for the proton using lattice QCD with twisted mass fermions, employing the pseudo-distribution approach to analyze systematic effects and obtain the x-dependence.

Contribution

It introduces a lattice QCD calculation of the gluon PDF using the twisted mass formulation and pseudo-distributions, providing new insights into gluon structure at near-physical pion mass.

Findings

Gluon PDF obtained at pion mass 260 MeV

Analysis of systematic effects related to Wilson line length

Data for nucleon momenta up to 1.67 GeV

Abstract

We present results of the x-dependence of the unpolarized gluon PDF for the proton. We use an $N_f=2+1+1$ ensemble of maximally twisted mass fermions with clover improvement and the Iwasaki improved gluon action. The quark masses are tuned so that the pion mass is 260 MeV. We use a $32^3\times64$ lattice size with a lattice spacing $a=0.093$ fm giving a spatial extent of 3 fm. We employ the pseudo-distribution approach and obtain the light-cone Ioffe time distribution (ITD) combining data for nucleon momentum boosts up to 1.67 GeV and Wilson line lengths, $z$, up to 0.56 fm. We explore systematic effects such as the dependence on the maximum value of $z$ entering the fits to obtain the gluon PDF.