Göttingen 2012 – scientific programme
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T: Fachverband Teilchenphysik
T 25: QCD 1
T 25.3: Talk
Monday, February 27, 2012, 17:25–17:40, ZHG 009
Quantification of Monte Carlo event generator scale-uncertainties with an example ATLAS analysis studying underlying event properties — Gerhard Brandt1, Frank Krauss2, Heiko Lacker3, Michael Leyton3, •Martin Mamach3, Holger Schulz3, and Daniel Weyh3 — 1University of Oxford — 2IPPP Durham — 3Humboldt University of Berlin
Monte Carlo (MC) event generators are widely employed in the analysis of experimental data also for LHC in order to predict the features of observables and test analyses with them. These generators rely on phenomenological models containing various parameters which are free in certain ranges. Variations of these parameters relative to their de- fault lead to uncertainties on the predictions of the event generators and, in turn, on the results of any experimental data analysis making use of the event generator. A Generalized method for quantifying a certain class of these generator based uncertainties will be presented in this talk. We study for the SHERPA event generator the effect on the analysis results from uncertainties in the choice of the merging and factorization scale. The quantification is done within an example ATLAS analysis measuring underlying event UE properties in Z-boson production limited to low transverse momenta (pTZ < 3 GeV) of the Z-boson. The analysis extracts event-shape distributions from charged particles in the event that do not belong to the Z decay for generate Monte Carlo event and data which are unfolded back to the generator level.