Nucleon Helicity and Transversity Parton Distributions from Lattice QCD

TL;DR

This paper reports the first lattice-QCD calculations of isovector polarized parton distribution functions, including helicity and transversity, using the LaMET approach to directly access Bjorken-x dependence, with implications for nucleon structure.

Contribution

It introduces a novel lattice-QCD methodology for directly computing polarized parton distributions with finite-momentum corrections and explores their phenomenological implications.

Findings

First lattice-QCD results for polarized PDFs using LaMET

Mass-correction formulation for all three cases

Predictions for sea-flavor asymmetry in transversely polarized nucleons

Abstract

We present the first lattice-QCD calculation of the isovector polarized parton distribution functions (both helicity and transversity) using the large-momentum effective field theory (LaMET) approach for direct Bjorken-$x$ dependence. We first review the detailed steps of the procedure in the unpolarized case, then generalize to the helicity and transversity cases. We also derive a new mass-correction formulation for all three cases. We then compare the effects of each finite-momentum correction using lattice data calculated at $M_\pi\approx 310$ MeV. Finally, we discuss the implications of these results for the poorly known antiquark structure and predict the sea-flavor asymmetry in the transversely polarized nucleon.