ELECTROMAGNETIC CONTRIBUTION TO THE NUCLEON SPIN

A possible resolution to the question of where the nucleon gets some p ortion of its internal angular momentum, not carried by the valence qu arks, is given in terms of the electromagnetic field angular momentum of the nucleon. This field angular momentum is similar in origin to th at of the Thomson dipole (an electric charge and a magnetic monopole), but arises from the interaction of the quark electric charges and mag netic dipoles. Rough, order of magnitude calculations show that such a field angular momentum could provide some of the nucleon's spin. Unde r assumptions similar to those used to calculate hadron mass splitting s, QCD should also exhibit a similar field angular momentum coming fro m the interaction of color charges with color magnetic dipoles. (C) 19 98 Published by Elsevier Science B.V. All rights reserved.