Master thesis defense by Pawel Klimek – Niels Bohr Institute - University of Copenhagen

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Master thesis defense by Pawel Klimek

Study of Z boson production using tau leptons final state in ATLAS


The start-up of the Large Hadron Collider (LHC) has began a new exciting period in particle physics. One of its independent particle detectors is ATLAS which is designed as a general purpose detector.

The goal of this project is to determine whether a pure sample of Z → τ+τ − events can be observed in ATLAS in the data collected during the first 100 pb−1 of collisions at 10 TeV. The final state considered is Z → τ+τ− → lepton νν hadron ν. All important backgrounds, including the severe QCD dijet production background, are considered. Several trigger and offline analysis strategies are presented, and an optimal choice is proposed, allowing a clear signal within the accumulated luminosity considered. The suggested selection allows to obtain a clear observation of Z → τ+τ− production, and therefore provides a data sample where the tau energy scale for hadronic tau lepton decays can be determined accurately in real data.

The presentation will consist of three main parts. In the first part the introduction to the Standard Model will be presented. The second part will present an overview of the ATLAS detector and its elements most relevant for the present studies. The final part will be an explanation of the analysis employed in the study.