Proton Isovector Helicity Distribution on the Lattice at Physical Pion Mass
Journal
Physical Review Letters
Journal Volume
121
Journal Issue
24
Date Issued
2018
Author(s)
Abstract
We present a state-of-the-art calculation of the isovector quark-helicity Bjorken-x distribution in the proton using lattice-QCD ensembles at the physical pion mass. We compute quasidistributions at proton momenta Pz{2.2,2.6,3.0} GeV on the lattice and match them systematically to the physical parton distribution using the large-momentum effective theory. We reach an unprecedented precision through high statistics in simulations, large-momentum proton matrix elements, and control of excited-state contamination. The resulting distribution with combined statistical and systematic errors is in agreement with the latest phenomenological analysis of the spin-dependent experimental data, in particular, Δū(x)>Δd(x).
Type
journal article