Nucleon Transversity Distribution at the Physical Pion Mass from Lattice QCD

TL;DR

This paper presents a high-precision lattice QCD calculation of the proton's isovector transversity distribution at the physical pion mass, providing insights into the quark spin structure with improved accuracy over experimental analyses.

Contribution

It introduces a state-of-the-art lattice QCD approach using LaMET and high proton momenta to accurately compute the transversity distribution, including nonperturbative renormalization and systematic control.

Findings

Provides the most precise theoretical prediction for large-x transversity distribution.

Finds sea quark asymmetry in transversity is consistent with zero.

Demonstrates the effectiveness of high-momentum lattice calculations for parton distributions.

Abstract

We report a state-of-the-art lattice calculation of the isovector quark transversity distribution of the proton at the physical pion mass. Within the framework of large-momentum effective theory (LaMET), we compute the transversity quasi-distributions using clover valence fermions on 2+1+1-flavor (up/down, strange, charm) HISQ-lattice configurations with boosted proton momenta as large as 3.0~GeV. The relevant lattice matrix elements are nonperturbatively renormalized in regularization-independent momentum-subtraction (RI/MOM) scheme and systematically matched to the physical transversity distribution. With high statistics, large proton momenta and meticulous control of excited-state contamination, we provide the best theoretical prediction for the large-$x$ isovector quark transversity distribution, with better precision than the most recent global analyses of experimental data. Our result also shows that the sea quark asymmetry in the proton transversity distribution is consistent with zero, which has been assumed in all current global analyses.