Physics of the gluon-helicity contribution to proton spin.
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.
INPAC, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China and Center for High-Energy Physics, Peking University, Beijing 100080, People's Republic of China and Maryland Center for Fundamental Physics, University of Maryland, College Park, Maryland 20742, USA.
Xiangdong
X
Ji
Jian-Hui
JH
Zhang
Yong
Y
Zhao