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T: Fachverband Teilchenphysik

T 26: QCD I

T 26.5: Talk

Monday, March 28, 2011, 17:45–18:00, 30.33: 001

Effects of Multiple-Parton-Interactions and Pile-up events — •Markus Schneider — DESY, Zeuthen

In proton-proton collision experiments, like ATLAS located at the Large Hadron Collider (LHC) at CERN, it is essential to understand, beside others, the so called Multiple-Parton-Interactions (MPI) and Pile-Up events in order to be able to make as precise measurements as possible. Multiple-Parton-Interactions are spectator-parton interactions additional to the 'hard' interaction between two partons coming from either of two colliding protons. Pile-Up events are proton-proton collisions additional to the 'hard' collision between two protons in one bunch-crossing. Within the ATLAS Multijets cross-section analysis, these two effects were studied with data as well as the help of the general-purpose Monte-Carlo Generators PYTHIA and HERWIG. In this talk, the effects are shown and compared qualitatively and quantitatively. Furtermore, possibilities to handle Pile-Up events are described more in detail. The mentioned effects, beside others (e.g. hadronization effects, detector effects, ...), have to be taken into account and one must correct for them. This procedure is called Unfolding and is also briefly presented for the multijets cross-section measurement.