Intrinsic transverse momentum and the polarized Drell-Yan process

In this paper we calculate the cross section at leading order in 1/Q for polarized Drell-Yan scattering at measured lepton-pair transverse momentum QT, using a field theoretical parton model approach. We find that for a hadron with spin 1/2 the quark content at leading order is described by six distribution functions for each flavor, which depend on both the light-cone momentum fraction x and the quark transverse momentum kT². These functions are illustrated for a free-quark ensemble. The cross sections for both longitudinal and transverse polarizations are expressed in terms of convolution integrals over the distribution functions.