The Underlying Event in Herwig++.

Stefan Gieseke, Christian Roehr & Andrzej Siodmok
We review the modelling of multiple interactions in the event generator \herwig{}++ and study implications of recent tuning efforts to LHC data. A crucial ingredient to a successful description of minimum-bias and underlying-event observables is a model for colour reconnection. Improvements to this model, inspired by statistical physics, are presented.