Measurement of the tt̅ cross section in pp̅ collisions at √s=1.96  TeV using dilepton events with a lepton plus track selection

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Aaltonen , T , Mehtälä , P , Orava , R , Mäki , T , Saarikko , H , Österberg , K & CDF Collaboration 2009 , ' Measurement of the tt̅ cross section in pp̅ collisions at √s=1.96  TeV using dilepton events with a lepton plus track selection ' , Physical Review D : Particles, Fields, Gravitation and Cosmology , vol. 79 , no. 11 , pp. 112007 . https://doi.org/10.1103/PhysRevD.79.112007

Title: Measurement of the tt̅ cross section in pp̅ collisions at √s=1.96  TeV using dilepton events with a lepton plus track selection
Author: Aaltonen, Timo; Mehtälä, Petteri; Orava, Risto; Mäki, Tuula; Saarikko, Heimo; Österberg, Kenneth; CDF Collaboration
Contributor: University of Helsinki, Helsinki Institute of Physics
University of Helsinki, Helsinki Institute of Physics
University of Helsinki, Helsinki Institute of Physics
University of Helsinki, Helsinki Institute of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2009
Language: eng
Number of pages: 41
Belongs to series: Physical Review D : Particles, Fields, Gravitation and Cosmology
ISSN: 1550-7998
URI: http://hdl.handle.net/10138/24411
Abstract: This paper reports a measurement of the cross section for the pair production of top quarks in ppbar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron. The data was collected from the CDF II detector in a set of runs with a total integrated luminosity of 1.1 fb^{-1}. The cross section is measured in the dilepton channel, the subset of ttbar events in which both top quarks decay through t -> Wb -> l nu b where l = e, mu, or tau. The lepton pair is reconstructed as one identified electron or muon and one isolated track. The use of an isolated track to identify the second lepton increases the ttbar acceptance, particularly for the case in which one W decays as W -> tau nu. The purity of the sample may be further improved at the cost of a reduction in the number of signal events, by requiring an identified b-jet. We present the results of measurements performed with and without the request of an identified b-jet. The former is the first published CDF result for which a b-jet requirement is added to the dilepton selection. In the CDF data there are 129 pretag lepton + track candidate events, of which 69 are tagged. With the tagging information, the sample is divided into tagged and untagged sub-samples, and a combined cross section is calculated by maximizing a likelihood. The result is sigma_{ttbar} = 9.6 +/- 1.2 (stat.) -0.5 +0.6 (sys.) +/- 0.6 (lum.) pb, assuming a branching ratio of BR(W -> ell nu) = 10.8% and a top mass of m_t = 175 GeV/c^2.
Subject: hep-ex
114 Physical sciences
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