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Title: Proton Isovector Helicity Distribution on the Lattice at Physical Pion Mass
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 quasi-distributions at proton momenta $P_z \in \{2.2, 2.6, 3.0\}$~GeV on the lattice, and match them systematically to the physical parton distribution using large-momentum effective theory (LaMET). We reach an unprecedented precision through high statistics in simulations, large-momentum proton matrix elements, and control of excited-state contamination. The resulting distribution is in agreement within $2\sigma$ with the latest phenomenological analysis of the spin-dependent experimental data; in particular, $\Delta \bar{u}(x)>\Delta \bar{d}(x)$.  more » « less
Award ID(s):
1653405
NSF-PAR ID:
10093085
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Date Published:
Journal Name:
Physical review letters
Volume:
121
Issue:
24
ISSN:
0031-9007
Page Range / eLocation ID:
242003
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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