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Title:Measurement of the top anti-top quark pair production cross section in the dilepton decay channel using Lepton+Track selection in 7 TeV p − p collisions with L = 698 PB−1
Author(s):Khandanyan, Hovhannes
Director of Research:Errede, Steven M.
Doctoral Committee Chair(s):Wiss, J.E.
Doctoral Committee Member(s):Errede, Steven M.; Stack, John D.; Cooper, S. Lance
Department / Program:Physics
Discipline:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Cross Section
Cross Section Measurement
Lepton+Track
Track-Lepton
ATLAS Cross Section
ATLAS Thesis
UIUC Thesis
UIUC ATLAS
Hovhannes
Khandanyan
Hovhannes Khandanyan Thesis
Hovhannes Khandanyan Dissertation
University of Illinois Champaign-Urbana (UIUC)
Abstract:We present measurements of the t¯t production cross section obtained using the ATLAS detector at the LHC with pp collisions at √s = 7 TeV in dilepton final states, from a data sample of L=698 pb−1 taken in 2011. For dilepton pair selection we have used a ‘Lepton+Track’ approach, where selection requirements on one lepton leg are reduced to a requirement of only a high quality Inner Detector track. This proce- dure, while allowing more background in the selected sample, enhances the sensitivity to τ-leptonic decays of the W± and increases the t¯t acceptance by 20% over the conventional dilepton analysis (where each lepton is identified as an electron or muon). Two modes of the l+track analysis were studied: the inclu- sive and the exclusive mode. The measured t¯t cross sections in the inclusive eTL and μTL channels are 182.9±9.3 (stat.)+21.9 −16.7 (syst.)+8.2 −7.3 (lum.) pb and 171.0±8.5 (stat.)+20.6 −17.5 (syst.)+7.8 −7.0 (lum.) pb, respectively. The inclusive eTL and μTL combined t¯t cross section is 177.4±6.3 (stat.)+18.4 −15.2 (syst.)±7.6 (lum.) pb. The mea- sured t¯t cross sections in the exclusive eTL and μTL channels are 160.8 ±22.6 (syst.)+45.1 −33.1 (syst.)+8.3 −6.8 (lum.) pb and 168.3 ± 23.9 (syst.)+45.8 −39.0 (syst.)+9.0 −7.5 (lum.) pb, respectively. The exclusive eTL and μTL combined t¯t cross section is 164.5 ± 16.4 (syst.)+39.0 −30.5 (syst.)+8.6 −7.1 (lum.) pb. These t¯t cross section measurements are consistent with each other and are in good agreement with the Standard Model prediction of 164.6+11.5 −15.8 pb.
Issue Date:2012-05-22
URI:http://hdl.handle.net/2142/30962
Rights Information:Copyright 2012 by Hovhannes Khandanyan. All rights reserved.
Date Available in IDEALS:2012-05-22
Date Deposited:2012-05


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