Third moments of nucleon unpolarized, polarized, and transversity parton distribution functions from physical-point lattice QCD

Abstract

Using forward matrix elements of local leading-twist operators, we present a determination of the isovector third Mellin moments ⟨ x 2 ⟩ of nucleon unpolarized, polarized, and transversity parton distribution functions. Two lattice QCD ensembles at the physical pion mass are used, which were generated using a tree-level Symanzik-improved gauge action and 2 + 1 flavor tree-level improved Wilson clover fermions coupling via two-level HEX smearing. Leveraging a wide set of operators, two extraction methods for the matrix elements, and the automatic inclusion of model uncertainties via bootstrapped model averages, we extract values of the third Mellin moments. This is the first direct calculation of these observables performed at the physical pion mass.