A critical assessment of the angular momentum sum rules
arXiv:1211.3957 · doi:10.1016/j.physletb.2013.01.050
Abstract
There are now five angular momentum relations or sum rules in the literature: the Jaffe, Manohar relation for a longitudinally polarized nucleon, and the Bakker, Leader, Trueman result for the case of transverse polarization; the Ji relation for longitudinal polarization, and the Leader result for transverse polarization, both involving generalized parton distributions; and a new sum rule due to Ji, Xiong and Yuan dealing with the transverse component of the Pauli-Lubanski vector. I discuss these various relations and examine their precise interpretation in the light of the so-called "angular momentum controversy". In particular, I show that the claim of Ji, Xiong and Yuan that their Pauli-Lubanski relation is frame or energy independent is incorrect, and that they have missed an energy dependent term in their expression.
14 pages. This version contains the following corrections to V2: Eq.~(23} is replaced by Eqs.~(23) and (24). Numerical factors have been corrected in various equations and, crucially, corrected in the old Eq.~(50), which now becomes (51)
References in corpus (4)
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