Relativistic spin sum rules and the role of the pivot

Abstract

Spin sum rules depend on the choice of a pivot, i.e. the point about which the angular momentun is defined, usually identified with the center of the nucleon. The latter is however not unique in a relativistic theory and has led to apparently contradictory results in the literature. Using the recently developed phase-space approach, we compute for the first time the contribution associated with the motion of the center of the nucleon, and we derive a general spin sum rule which reduces to established results after appropriate choices for the pivot and the spin component.

16 pages, 1 figure, 1 table

References in corpus (2)

• Rigorous constraints on the matrix elements of the energy-momentum tensor
• Transverse spin sum rule of the proton

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• Transverse energy-momentum tensor distributions in polarized nucleons