Confronting lattice parton distributions with global QCD analysis

TL;DR

This paper integrates lattice QCD data into a global analysis of parton distribution functions, revealing limited constraints for unpolarized PDFs but strong agreement and constraints for polarized PDFs, advancing the understanding of nucleon structure.

Contribution

It introduces the first Monte Carlo global QCD analysis incorporating lattice QCD matrix elements, assessing universality and consistency between lattice and experimental data.

Findings

Weak constraints on unpolarized PDFs from lattice data

Good agreement for polarized PDFs between lattice and experiment

Lattice data significantly constrains spin-dependent distributions

Abstract

We present the first Monte Carlo based global QCD analysis of spin-averaged and spin-dependent parton distribution functions (PDFs) that includes nucleon isovector matrix elements in coordinate space from lattice QCD. We investigate the degree of universality of the extracted PDFs when the lattice and experimental data are treated under the same conditions within the Bayesian likelihood analysis. For the unpolarized sector, we find rather weak constraints from the current lattice data on the phenomenological PDFs, and difficulties in describing the lattice matrix elements at large spatial distances. In contrast, for the polarized PDFs we find good agreement between experiment and lattice data, with the latter providing significant constraints on the spin-dependent isovector quark and antiquark distributions.