Prof. Dr. Judith Katzy

The leftovers: physics of beam remnant and multi-parton interaction

Physics processes at the LHC are typically described by Feynman graphs that start with the gluon and quarks initiating the process. But LHC does not directly collide quarks and gluons - it collides protons which contain plenty of quarks and gluons. So what happens to the rest that is not involved in the hard scatter process? 

In this talk I will discuss phenomenological models to describe multi-parton interactions and beam remnant models for proton proton collisions using the examples the models implemented in the multi-purpose Monte Carlo generators PYTHIA and Herwig. I will show measurements sensitive to these models from LEP and LHC and how they are used to adopt the free parameters in the model, i.e. tune the predictions. I will also describe hadronisation models that combines the quarks and gluons to the hadrons we observe.