Transverse momentum-dependent parton distributions for longitudinally polarized nucleons from domain wall fermion calculations at the physical pion mass

TL;DR

This paper presents lattice QCD calculations of the helicity and worm-gear TMDs for longitudinally polarized nucleons using domain wall fermions at the physical pion mass, filling a gap in previous studies focused on transverse polarization.

Contribution

It introduces the first lattice QCD evaluation of longitudinally polarized nucleon TMDs, specifically the helicity and worm-gear TMDs, using a domain wall fermion ensemble at the physical pion mass.

Findings

First lattice QCD results for these TMDs at physical pion mass.

Provides insights into the internal spin structure of nucleons.

Utilizes staple-shaped gauge connections for TMD definitions.

Abstract

Previous Lattice QCD calculations of nucleon transverse momentum-dependent parton distributions (TMDs) focused on the case of transversely polarized nucleons, and thus did not encompass two leading-twist TMDs associated with longitudinal polarization, namely, the helicity TMD and the worm-gear TMD corresponding to transversely polarized quarks in a longitudinally polarized nucleon. Based on a definition of TMDs via hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections, TMD observables characterizing the aforementioned two TMDs are evaluated, utilizing an RBC/UKQCD domain wall fermion ensemble at the physical pion mass.