Contribution invited talk
On the lepton azimuthal angular distributions in the Drell-Yan process
The lepton angular distributions of the Drell-Yan process in fixed-target experiments and the Z-boson production at colliders are investigated by NLO and NNLO perturbative QCD and an intuitive geometric approach. The main features of the kinematic dependencies of the angular distributions coefficients can be well understood in the geometrical approach. Implications of this approach on the rotational invariance of the angular coefficients, the behavior of the coefficients for Z plus jets events, and the extraction of the Boer-Mulders functions from the Drell-Yan process will be presented.