Würzburg 2018 – scientific programme

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T: Fachverband Teilchenphysik

T 19: Top-Quarks: Produktion II

T 19.5: Talk

Monday, March 19, 2018, 17:00–17:15, Z6 - SR 2.011

Monte-Carlo generators for top-quark pair production in the ATLAS experiment — •Timothée Theveneaux-Pelzer — DESY, Zeuthen, Germany

To study top-quark pair production (tt) in proton-proton data at the LHC, Monte-Carlo (MC) generators are needed to model this process accurately. This is the case either when tt is the signal - in order to model the detector acceptance and response in high-precision measurements - or when tt is one of the backgrounds - in order to model several event variables in various regions of phase-space.

MC generators are in general made of several components, each with many parameters which values can’t be deduced by first principles. Therefore, a MC generator have to be wisely optimised (or tuned) in order to provide an accurate description of the desired process. This optimisation can take advantage of inputs from both theoretical predictions and experimental measurements.

The ATLAS collaboration performed several studies on tt MC generators since run-1. The latest model is based on the Powheg-Box Next-to-Leading Order matrix element generator, in association with Pythia8 for parton shower and hadronisation. In this talk, the optimisation of this model and the associated uncertainties will be described, and a brief overview of possible future improvements will also be given.