Towards High-Precision Parton Distributions From Lattice QCD via Distillation

TL;DR

This paper uses the distillation technique in lattice QCD to improve the extraction of the nucleon's valence PDF, revealing deviations from expected evolution that are addressed through discretization corrections.

Contribution

It introduces a novel application of distillation for high-precision PDF extraction and develops a new method to derive PDFs from pITD, highlighting the importance of discretization effects.

Findings

Improved determination of Ioffe-time Pseudo-distribution (pITD)

Observed deviations from DGLAP evolution in pITD

Discretization corrections restore expected evolution behavior

Abstract

We apply the Distillation spatial smearing program to the extraction of the unpolarized isovector valence PDF of the nucleon. The improved volume sampling and control of excited-states afforded by distillation leads to a dramatically improved determination of the requisite Ioffe-time Pseudo-distribution (pITD). The impact of higher-twist effects is subsequently explored by extending the Wilson line length present in our non-local operators to one half the spatial extent of the lattice ensemble considered. The valence PDF is extracted by analyzing both the matched Ioffe-time Distribution (ITD), as well as a direct matching of the pITD to the PDF. Through development of a novel prescription to obtain the PDF from the pITD, we establish a concerning deviation of the pITD from the expected DGLAP evolution of the pseudo-PDF. The presence of DGLAP evolution is observed once more following introduction of a discretization term into the PDF extractions. Observance and correction of this discrepancy further highlights the utility of distillation in such structure studies.