Transverse momentum in double parton scattering

We discuss elements of the framework needed for describing single parton scattering (SPS) processes such as e.g. Drell-Yan. In our description we go beyond the ordinary collinear parton distribution functions (PDFs) and consider transverse momentum dependent PDFs (TMDs), for which we show some selected results. Our goal is to generalize the SPS treatment of processes with a colorless final state towards double parton scattering (DPS), where two pairs of partons from the same hadronic collision interact in two independent hard processes. This requires addressing the role of color in DPS as well as handling the more complicated structure of the soft function. Then, for transverse momentum dependent DPS the cross section involves transverse momentum dependent double parton distributions (DTMDs). We present the evolution equations for DTMDs and their solutions in the region of perturbative transverse momentum and a large transverse distance between the two partons.