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Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Experimentelle Elementarteilchenphysik

Humboldt-Universität zu Berlin | Mathematisch-Naturwissen­schaft­liche Fakultät | Institut für Physik | Experimentelle Elementarteilchenphysik | ATLAS | Theses | Studien zur Abschätzung des QCD-Untergrundes elektroschwacher Top-Produktion bei ATLAS

Umberto Prosperi Porta (2012)

Studien zur Abschätzung des QCD-Untergrundes elektroschwacher Top-Produktion bei ATLAS

Master thesis, Humboldt-Universität zu Berlin.

One of the major research areas of the top-physics at ATLAS consists in measuring the electroweak production of single t-quark in t-channel. In this thesis two methods to estimate the QCD-background of the single-top-physics of the p p-collisions at ATLAS are presented: the matrix method and the jet-electron-method. The QCD-background of the single-top-production is mainly due to the misidentification of leptons, which originate from decays of t-quarks, with jets. Hence, the QCD-reconstruction is based on those events, which are counted as single-top-events as a result of lepton-misidentification. Both presented methods are data driven because of the inefficiency of the available Monte-Carlo-simulations in describing the misidentified leptons. The analysis is carried out in both electron and muon channels applying the kinematic fit implemented at the Humbold-Universität zu Berlin and using the data collected in 2011 for a centre-of-mass energy of 7 TeV and an integrated luminosity of 4,7 pb-1 . In addition, the results of the calculation of the covariance matrices used by the kinematic fit are discussed. Estimating the QCD-background is necessary to perform the single-top-analysis and, consequently, worthwhile to help search for new physics beyond the Standard Model. For these reasons, the QCD-estimation is a relevant topic for the ATLAS collaboration.