Abstract

We perform an analysis of the quark angular momentum in a light-cone representation by taking into account the effect due to the Melosh-Wigner rotation and find that there is a relativistic correction factor connecting the quark orbital angular momentum with the quark model spin distribution: Lq(x) = (ML(x))?qQM(x). The quark orbital angular momentum Lq(x) and the quark helicity distribution ?q(x) are connected to the quark model spin distribution ?qQM(x) by a relation 1/2?q(x) + Lq(x) = 1/2?QM(x), which means that one can decompose the quark model spin contribution ?qQM(x) by a quark helicity term ?q(x) plus an orbital angular momentum term Lq(x). There is also a new relation connecting the quark orbital angular momentum with the measurable quark helicity distribution and transversity distribution (?q(x)): ?q(x) + Lq(x) = ?q(x), from which we may have new sum rules connecting the quark orbital angular momentum with the nucleon axial and tensor charges.