Smeared quasidistributions in perturbation theory

Abstract

Quasi and pseudo distributions provide a new approach to determining parton distribution functions (PDFs) from first principles' calculations of quantum chromodynamics (QCD). Here I calculate the flavor nonsinglet unpolarized quasi distribution at one loop in perturbation theory, using the gradient flow to remove ultraviolet divergences. I demonstrate that, as expected, the gradient flow does not change the infrared structure of the quasi distribution at one loop and use the results to match the smeared matrix elements to those in the $\ms$ scheme. This matching calculation is required to relate numerical results obtained from nonperturbative lattice QCD computations to light-front PDFs extracted from global analyses of experimental data.