Orbital angular momentum parton distributions in light-front dynamics - art. no. 054023

We study the quark angular momentum distribution in the nucleon within a li ght-front covariant quark model. Special emphasis is put into the orbital a ngular momentum, a quantity which is very sensitive to the relativistic tre atment of the spin in a light-front dynamical approach. Discrepancies with the predictions of the low-energy traditional quark models where relativist ic spin effects are neglected are visible also after perturbative evolution to higher momentum scales. Orbital angular momentum distributions and thei r contribution to the spin sum rule are calculated for different phenomenol ogical mass operators and compared with the results of the MIT bag model.