Quark orbital-angular-momentum distribution in the nucleon - art. no. 014013.

We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. F rom the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark orbital angular momentum distribution L-q(x). The l atter can be extracted from data on the polarized and unpolarized quark dis tributions and the off-forward distribution E(x) in the forward limit. We c omment upon the evolution equations obeyed by this as well as other orbital distributions considered in the literature. [S0556-2821(99)02501-1].