Parton Orbital Angular Momentum and Final State Interactions

TL;DR

This paper explores the relationship between different definitions of quark orbital angular momentum in nucleons, linking theoretical frameworks with experimental phenomena like single-spin asymmetries.

Contribution

It clarifies the connection between Ji and Jaffe-Manohar definitions of orbital angular momentum using Wigner distributions and interprets their difference through final state interactions.

Findings

The difference between the two definitions corresponds to the change in orbital angular momentum during DIS.

Final state interactions are responsible for the observed change in quark orbital angular momentum.

The mechanism is similar to that causing transverse single-spin asymmetries.

Abstract

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 as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.