Boer-Mulders function of the pion and the qT-weighted cos 2φ asymmetry in the unpolarized π-p Drell-Yan process at COMPASS

We calculate the two leading-twist transverse momentum dependent distribution functions of the pion meson, the unpolarized distribution f(1 pi)(x, k(T)(2)) and the Boer-Mulders function h(1 pi)(perpendicular to) (x,k(T)(2)), using the pion wave functions derived from a light-cone approach. The evolution effect of the first k(T)-moment of the pion Boer-Mulders function is studied by employing an approximate evolution kernel. Using the model resulting distributions, we predict the transverse momentum weighted cos 2 phi azimuthal asymmetry in the unpolarized pi(-) p Drell-Yan process which can be measured at COMPASS in the near future.