Probing relativistic spin effects in the nucleon by means of Drell-Yan processes - art. no. 094018

Significant differences between transverse and longitudinal polarized parto n distributions are found at low energies within a light-front covariant qu ark model of the nucleon. These differences are due to relativistic spin ef fects introduced by the Melosh rotations and survive evolution to higher Q( 2) scales. A specific observable related to double-spin asymmetries in lept on pair production in polarized hadron-hadron collisions is defined. The po ssibility of assessing the relevance of these relativistic spin effects in future experiments at BNL RHIC and DESY HERA-(N) over right arrow is discus sed.