Quark and gluon orbital angular momentum and spin in hard processes Original Research Article

We suggest a method of constructing gauge-invariant quark and gluon distributions that describe an abstract QCD observable and apply this method to analyze angular momentum of a hadron. In addition to the known quark and gluon polarized structure functions, we obtain gauge-invariant distributions for quark and gluon orbital angular momenta, and consider some basic properties of these distributions and their moments.