Electromagnetic Form Factors and the Localization of Quark Orbital Angular Momentum in the Proton

Abstract

A new picture is given of generalized parton distributions probed in experiments in which the probe scale $Q^2$ and the momentum transfer ${\text{DD}}^2$ are well separated. Application of this picture to the $Q^2$ dependence of the form factors $F_1,F_2$ shows that gauge invariant quark orbital angular momentum can be measured and indeed {\it localized} in the transverse profile of the proton. A previous prediction that $\sqrt{Q^2}{F}_2(Q^2)/F_1(Q^2)\sim const.$ is generalized to GPD language. This prediction appears to have been confirmed by recent CEBAF data.

Comments: 6 pages, 1 figure. To appear in DIS 2001, 9th International Workshop on Deep Inelastic Scattering, Bologna, 27 April - 1 May, 2001