Azimuthal asymmetry in unpolarized πN Drell-Yan process

Taking into account the effect of final-state interaction, we calculate the non-zero (naïve) T-odd transverse momentum dependent distribution h1⊥(x,k⊥2) of the pion in a quark-spectator-antiquark model with effective pion-quark-antiquark coupling as a dipole form factor. Using the model result we estimate the cos2ϕ asymmetries in the unpolarized π−N Drell-Yan process which can be expressed as h1⊥×h¯1⊥. We find that the resulting h1π⊥(x,k⊥2) has the advantage to reproduce the asymmetry that agrees with the experimental data measured by NA10 Collaboration. We estimate the cos2ϕ asymmetries averaged over the kinematics of NA10 experiments for 140, 194 and 286 GeV π− beam and compare them with relevant experimental data.