Probing transverse-momentum distributions with the Drell-Yan process

The Drell-Yan process offers access, complementary to deep inelastic scattering (DIS) to the transverse-momentum distributions of the quarks within a hadron. When neither the beam nor the target are polarized, the angular distributions of Drell-Yan scattering provide access to the h(1)(perpendicular to), Boer-Mulders, distribution. With the addition of either a polarized beam or target, other transverse-momentum distributions (TMDs) can be accessed, in particular the Sivers' distribution, f(1)(perpendicular to). Existing Boer-Mulders and planned Sivers' Drell-Yan measurements of these distributions are discussed.