Partonic Transverse Motion in Unpolarized Semi-Inclusive Deep Inelastic   Scattering Processes
  We analyse the role of partonic transverse motion in unpolarized Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes. Imposing appropriate kinematical conditions, we find some constraints which fix an upper limit to the range of allowed k_perp values. We show that, applying these additional requirements on the partonic kinematics, we obtain different results with respect to the usual phenomenological approach based on the Gaussian smearing with analytical integration over an unlimited range of k_perp values. These variations are particularly interesting for some observables, like the < cos phi_h > azimuthal modulation of the unpolarized SIDIS cross section or the average transverse momentum of the final, detected hadron. 
M. Boglione, S. Melis, A. Prokudin
hep-ph hep-ex