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Development of a Data-Driven Algorithm to Determine the W+Jets Background in Top-Antitop Events in ATLAS

The physics of the top quark is one of the key components in the physics programme of the ATLAS experiment at the Large Hadron Collider at CERN. In this thesis, general studies of the jet trigger performance for top quark events using fully simulated Monte Carlo samples are presented and two data-dr...

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Autor principal: Mehlhase, Sascha
Lenguaje:eng
Publicado: 2013
Materias:
Acceso en línea:http://cds.cern.ch/record/1503568
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author Mehlhase, Sascha
author_facet Mehlhase, Sascha
author_sort Mehlhase, Sascha
collection CERN
description The physics of the top quark is one of the key components in the physics programme of the ATLAS experiment at the Large Hadron Collider at CERN. In this thesis, general studies of the jet trigger performance for top quark events using fully simulated Monte Carlo samples are presented and two data-driven techniques to estimate the multi-jet trigger efficiency and the W+Jets background in top pair events are introduced to the ATLAS experiment. In a tag-and-probe based method, using a simple and common event selection and a high transverse momentum lepton as tag object, the possibility to estimate the multijet trigger efficiency from data in ATLAS is investigated and it is shown that the method is capable of estimating the efficiency without introducing any significant bias by the given tag selection. In the second data-driven analysis a new method to estimate the W+Jets background in a top-pair event selection is introduced to ATLAS. By defining signal and background dominated regions by means of the jet multiplicity and the pseudo-rapidity distribution of the lepton in the event, the W+Jets contribution is extrapolated from the background dominated into the signal dominated region. The method is found to estimate the given background contribution as a function of the jet multiplicity with an accuracy of about 25% for most of the top dominated region with an integrated luminosity of above 100 pb${}^{−1}$ at $\sqrt{s}=10$ TeV. This thesis also covers a study summarising the thermal behaviour and expected performance of the Pixel Detector of ATLAS. All measurements performed during the commissioning phase of 2008/09 yield results within the specification of the system and the performance is expected to stay within those even after several years of running under LHC conditions.
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spelling cern-15035682019-09-30T06:29:59Zhttp://cds.cern.ch/record/1503568engMehlhase, SaschaDevelopment of a Data-Driven Algorithm to Determine the W+Jets Background in Top-Antitop Events in ATLASParticle Physics - ExperimentThe physics of the top quark is one of the key components in the physics programme of the ATLAS experiment at the Large Hadron Collider at CERN. In this thesis, general studies of the jet trigger performance for top quark events using fully simulated Monte Carlo samples are presented and two data-driven techniques to estimate the multi-jet trigger efficiency and the W+Jets background in top pair events are introduced to the ATLAS experiment. In a tag-and-probe based method, using a simple and common event selection and a high transverse momentum lepton as tag object, the possibility to estimate the multijet trigger efficiency from data in ATLAS is investigated and it is shown that the method is capable of estimating the efficiency without introducing any significant bias by the given tag selection. In the second data-driven analysis a new method to estimate the W+Jets background in a top-pair event selection is introduced to ATLAS. By defining signal and background dominated regions by means of the jet multiplicity and the pseudo-rapidity distribution of the lepton in the event, the W+Jets contribution is extrapolated from the background dominated into the signal dominated region. The method is found to estimate the given background contribution as a function of the jet multiplicity with an accuracy of about 25% for most of the top dominated region with an integrated luminosity of above 100 pb${}^{−1}$ at $\sqrt{s}=10$ TeV. This thesis also covers a study summarising the thermal behaviour and expected performance of the Pixel Detector of ATLAS. All measurements performed during the commissioning phase of 2008/09 yield results within the specification of the system and the performance is expected to stay within those even after several years of running under LHC conditions.CERN-THESIS-2010-278oai:cds.cern.ch:15035682013-01-08T19:50:36Z
spellingShingle Particle Physics - Experiment
Mehlhase, Sascha
Development of a Data-Driven Algorithm to Determine the W+Jets Background in Top-Antitop Events in ATLAS
title Development of a Data-Driven Algorithm to Determine the W+Jets Background in Top-Antitop Events in ATLAS
title_full Development of a Data-Driven Algorithm to Determine the W+Jets Background in Top-Antitop Events in ATLAS
title_fullStr Development of a Data-Driven Algorithm to Determine the W+Jets Background in Top-Antitop Events in ATLAS
title_full_unstemmed Development of a Data-Driven Algorithm to Determine the W+Jets Background in Top-Antitop Events in ATLAS
title_short Development of a Data-Driven Algorithm to Determine the W+Jets Background in Top-Antitop Events in ATLAS
title_sort development of a data-driven algorithm to determine the w+jets background in top-antitop events in atlas
topic Particle Physics - Experiment
url http://cds.cern.ch/record/1503568
work_keys_str_mv AT mehlhasesascha developmentofadatadrivenalgorithmtodeterminethewjetsbackgroundintopantitopeventsinatlas