Nucleon transverse quark spin densities

TL;DR

This paper calculates nucleon transverse quark spin densities using lattice QCD with physical quark masses, providing detailed form factors and tensor charges, and extrapolating results to the continuum limit.

Contribution

It presents the first lattice QCD calculation of Mellin moments of nucleon transverse quark spin densities with physical quark masses and continuum extrapolation.

Findings

Computed isovector transverse quark spin densities.

Provided tensor charge results for each quark flavor.

Included disconnected contributions for the tensor charge.

Abstract

We present a calculation of the Mellin moments of the nucleon transverse quark spin densities extracted from the unpolarized and transversity generalized form factors. We use three $N_F=2+1+1$ ensembles of twisted mass fermions with quark masses tuned to their physical values and lattice spacings $a\sim 0.08$~fm, $a\sim 0.07$~fm and $a\sim 0.06$~fm and extrapolate the form factors to the continuum limit. Besides isovector densities we also include results for the tensor charge for each quark flavor using the ensemble with $a\sim 0.08$~fm for which we include the disconnected contributions.