Initial-state showering from QCD colour dipoles

In my talk I briefly present my work on a QCD colour dipole cascade, which is planned to be made available within the Monte Carlo event generator SHERPA. In particular for the case of initial-state radiation, I have developed a new approach, which is alternative to the Lund Group's colour dipole model. Here, I use a completely perturbative ansatz, where colour dipoles are also spanned with incoming parton lines, yielding two new types of dipoles, initial-initial and initial-final ones. Starting from the hard process, at no point in the evolution down to the cut-off scale, the beam remnants will be included; this part is entirely left to the hadronization. The main tasks that had to be solved for the new dipole types can be summarized by identifying the 2→3 splitting functions, finding suitable evolution variables and, from them, setting up the onshell-kinematics for the three new momenta. I present some first results for Drell-Yan production at a hadron collider, which have been obtained with this new shower algorithm. (orig.)