The Drell-Yan measurement at COMPASS-II

The Drell-Yan process can be used to access Transverse Momentum Dependent Parton Distribution Functions, such as the Boer-Mulders and the Sivers functions, and the transversity function, providing complementary information to what is known from Semi Inclusive Deep Inelastic Scattering data. The COMPASS experiment offers the possibility to study single polarized Drell-Yan processes (π− + p↑ → μ+μ− + X), making use of its large acceptance spectrometer and its unique transversely polarised proton target. A fundamental test of the factorization theorem in the non-perturbative QCD can be performed as well, by verifying the sign change of the Boer-Mulders and the Sivers functions depending if they are accessed via SIDIS or Drell-Yan process. The future Drell-Yan experiment at COMPASS is foreseen in late 2014.