Measurement of the Top Quark Pair Production Cross Section and Simultaneous Extraction of the W Heavy Flavor Fraction at √s = 7 TeV with the ATLAS Detector at the LHC

Messung des Top-Quark-Paar Wirkungsquerschnitts und gleichzeitige Bestimmung des W Heavy Flavor Anteils bei √s = 7 TeV mit dem ATLAS Detektor am LHC

by Adam Roe
Doctoral thesis
Date of Examination:2012-03-22
Date of issue:2012-04-27
Advisor:Prof. Dr. Arnulf Quadt
Referee:Prof. Dr. Arnulf Quadt
Referee:PD Dr. Jörn Große-Knetter
Referee:Prof. Dr. Steffen Schumann
Persistent Address: http://dx.doi.org/10.53846/goediss-2968

 

 

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Abstract

English

The top quark pair production cross section, σtt, is measured in the semileptonic channel in two datasets using a binned profiled likelihood template fit to data to discriminate the signal, tt, from its main background, the production of a W-boson in association with jets (W+jets). Templates in the first analysis are derived from a four variable flavor-sensitive discriminant to measure σtt in ∫ L dt = 35 pb-1. A similar but flavor-insensitive discriminant is then used to measure σtt in ∫ L dt = 0.7 fb-1. A third analysis is presented which simultaneously fits the fractions of tt and W+jets events in which heavy flavor jets are produced, using a single flavor-sensitive distribution in the ∫ L dt = 0.7 fb-1 dataset. Experimental precision of the top quark pair production cross section surpasses the theoretical uncertainty. No significant deviations from predictions are found but the results are higher than expectation.
Keywords: Particle Physics; Top Quark; ATLAS; LHC; cross section; production cross section
Schlagwörter: Teilchenphysik; Top Quark; ATLAS; LHC; Wirkungsquerschnitt; quershnitt
 
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