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 P-z is an element of {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 ...
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 P-z is an element of {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, Delta(u) over bar (x) > Delta(d) over bar (x).
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