Gluon Pseudo-Distributions at Short Distances: Forward Case

TL;DR

This paper develops a theoretical framework for extracting gluon PDFs from lattice QCD calculations using the pseudo-PDF approach, including one-loop calculations and matching relations.

Contribution

It provides a classification of gluon correlators, performs one-loop calculations in a gauge-invariant form, and derives matching relations between lattice data and gluon PDFs.

Findings

Separated UV and IR sources of $ ext{ln}(-z^2)$ dependence.

Derived matching relation between reduced ITD and light-cone ITD.

Facilitated calculation of one-loop matching for quasi-PDFs.

Abstract

We present the results that are necessary in the ongoing lattice calculations of the gluon parton distribution functions (PDFs) within the pseudo-PDF approach. We give a classification of possible two-gluon correlator functions and identify those that contain the invariant amplitude determining the gluon PDF in the light-cone $z^2 \to 0$ limit. One-loop calculations have been performed in the coordinate representation and in an explicitly gauge-invariant form. We made an effort to separate ultraviolet (UV) and infrared (IR) sources of the $\ln (-z^2)$-dependence at short distances $z^2$. The UV terms cancel in the reduced Ioffe-time distribution (ITD), and we obtain the matching relation between the reduced ITD and the light-cone ITD. Using a kernel form, we get a direct connection between lattice data for the reduced ITD and the normalized gluon PDF. We also show that our results may be used for a rather straightforward calculation of the one-loop matching relations for quasi-PDFs.