We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of Chen et al. are the same as those whose matrix elements correspond to the moments of generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally and discuss the strategies of calculating them in lattice QCD.
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This work is partially supported by U.S. Department of Energy Grants No. DE-SC0013065 and No. DE-FG02-93ER-40762.
Zhao, Yong; Liu, Keh-Fei; and Yang, Yi-Bo, "Orbital Angular Momentum and Generalized Transverse Momentum Distribution" (2016). Physics and Astronomy Faculty Publications. 449.