Flavor separation of the Boer-Mulders function from unpolarized π-p and π-D Drell-Yan processes

We show that measuring the cos2 phi angular dependence in unpolarized Drell-Yan processes with pi(-) beams colliding on proton and deuteron targets can determine the ratio of the Boer-Mulders functions for d and u quarks inside the proton h(1)(perpendicular to,d)/h(1)(perpendicular to,u), which is still lack of theoretical constraint. The comparison of the cos2 phi asymmetries measured in unpolarized pi(-)p and pi D- Drell-Yan processes, which are accessible at CERN by the COMPASS Collaboration, can help to discriminate whether h(1)(perpendicular to) effects or QCD vacuum effects are preferred by data. (c) 2006 Published by Elsevier B.V.