Single transverse spin asymmetries in inclusive hadron production

A consistent phenomenological approach to the computation of transverse sin gle spin asymmetries in inclusive hadron production is presented, based on the assumed generalization of the QCD factorization theorem to the case in which quark intrinsic motion is taken into account. New Icl and spin depend ent quark distribution and fragmentation functions are considered: some of them are fixed by fitting data on p(up arrow)p --> pi X and predictions are given for single spin asymmetries in lp(up arrow) --> pi X and gamma*p(up arrow) --> pi X processes.