Ji X, Zhang JH, Zhao Y. Physics of the gluon-helicity contribution to proton spin.
PHYSICAL REVIEW LETTERS 2013;
111:112002. [PMID:
24074075 DOI:
10.1103/physrevlett.111.112002]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Indexed: 06/02/2023]
Abstract
The total gluon helicity in a polarized proton, measurable in high-energy scattering, is shown to be the large momentum limit of a gauge-invariant but nonlocal, frame-dependent gluon spin E × A⊥ in QCD. This opens a door for a nonperturbative calculation of this quantity in lattice QCD and also justifies using free-field expressions in the light-cone gauge as physical observables.
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