A Lattice Calculation of Parton Distributions

TL;DR

This paper uses lattice QCD with quasi-distributions to calculate the x-dependent parton distributions in the proton, improving accuracy and exploring polarized distributions revealing sea quark asymmetries.

Contribution

It presents the first lattice QCD calculations of polarized parton distributions using quasi-distributions, with reduced errors and new insights into sea quark asymmetries.

Findings

Reduced errors by a factor of 2.5 compared to previous work.

First results for polarized distributions showing sea quark asymmetries.

Indications of u antiquark dominance in helicity and d antiquark in transversity distributions.

Abstract

We present results for the $x$ dependence of the unpolarized, helicity, and transversity isovector quark distributions in the proton using lattice QCD, employing the method of quasi-distributions proposed by Ji in 2013. Compared to a previous calculation by us, the errors are reduced by a factor of about 2.5. Moreover, we present our first results for the polarized sector of the proton, which indicate an asymmetry in the proton sea in favor of the $u$ antiquarks for the case of helicity distributions, and an asymmetry in favor of the $d$ antiquarks for the case of transversity distributions.