The Nucleon Spin Sum Rule

Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum due to final state interactions as it leaves the target in a DIS experiment.
6 pages, invited talk at 3rd Workshop on the QCD Structure of the Nucleon (QCD-N'12)