Spin-Orbit Dynamics from the Gluon Asymmetry
  Determination of the orbital angular momentum of the proton is a difficult but important part of understanding fundamental structure. Insight can be gained from suitable models of the gluon asymmetry applied to the Jz = 1/2 sum rule. We have constrained the models of the asymmetry to gain possible scenarios for the angular momentum of the proton's constituents. Results and phenomenology for determining Lz are presented. 
Gordon P. Ramsey (Loyola U and Argonne National Lab), Yev Binder and   Dennis Sivers