Drell-Yan processes, transversity and light-cone wavefunctions

The unpolarized, helicity and transversity distributions of quarks in the proton are calculated in the overlap representation of light-cone wavefunctions truncated to the lowest order Fock-space components with three valence quarks. The three distributions at the hadronic scale satisfy an interesting relation consistent with the Soffer inequality. Results are derived in a relativistic quark model including radiative corrections up to the next-to-leading order. Predictions for the double transverse-spin asymmetry in Drell-Yan dilepton production initiated by proton-antiproton collisions are presented. Asymmetries of about 20-30% are found in the kinematic conditions of the PAX experiment.