Quark Contributions to Nucleon Momentum and Spin from Domain Wall fermion calculations

TL;DR

This paper uses domain wall fermion calculations to analyze the contributions of light quarks to the nucleon’s spin and momentum, revealing cancellations and form factor behaviors consistent with previous studies.

Contribution

It provides new lattice QCD results on quark spin and orbital angular momentum contributions using dynamical domain wall fermions at near-physical pion masses.

Findings

Opposite spin and orbital angular momenta for u and d quarks.

Almost complete cancellation of d quark contributions.

Minimal variation of generalized form factors with pion mass.

Abstract

We report contributions to the nucleon spin and momentum from light quarks calculated using dynamical domain wall fermions with pion masses down to 300 MeV and fine lattice spacing a=0.084 fm. Albeit without disconnected diagrams, we observe that spin and orbital angular momenta of both u and d quarks are opposite, almost canceling in the case of the d quark, which agrees with previous calculations using a mixed quark action. We also present the full momentum dependence of n=2 generalized form factors showing little variation with the pion mass.