Flavor separation of the Boer-Mulders function from unpolarized ${\pi }^{-}p$ and ${\pi }^{-}D$ Drell-Yan processes

Abstract

We show that measuring the $\cos 2\varphi$ 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 $h_1^{\perp ,d}/h_1^{\perp ,u}$, which is still lack of theoretical constraint. The comparison of the $\cos 2\varphi$ 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 $h_1^{\perp }$ effects or QCD vacuum effects are preferred by data.

Comments: 10 pages, 2 figures, published in Physics Letters B