Partonic Transverse Motion in Unpolarized Semi-Inclusive Deep Inelastic   Scattering
  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 kt values and lead to interesting results, particularly for some observables like the <cos phi_h> azimuthal modulation of the unpolarized SIDIS cross section and the average transverse momentum of the final, detected hadron. 
M. Boglione, S. Melis, A. Prokudin
hep-ph