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

Titel: Measurement of the tt̅ cross section in pp̅ collisions at √s=1.96  TeV using dilepton events with a lepton plus track selection
Sekundär titel: A Measurement of the t-tbar Cross Section in p-pbar Collisions at sqrt(s) = 1.96 TeV using Dilepton Events with a Lepton plus Track Selection
Författare: Aaltonen, Timo; Mehtälä, Petteri; Orava, Risto; Mäki, Tuula; Saarikko, Heimo; Österberg, Kenneth; CDF Collaboration
Upphovmannens organisation: Helsinki Institute of Physics
Particle Physics and Astrophysics
Department of Physics
Datum: 2009
Språk: eng
Sidantal: 41
Tillhör serie: Physical Review D : Particles, Fields, Gravitation and Cosmology
ISSN: 1550-7998
DOI: https://doi.org/10.1103/PhysRevD.79.112007
Permanenta länken (URI): http://hdl.handle.net/10138/24411
Abstrakt: 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.This paper reports a measurement of the cross section for the pair production of top quarks in pp̅ collisions at √s=1.96  TeV at the Fermilab Tevatron. The data were collected from the CDF run 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 tt̅ events in which both top quarks decay through t→Wb→ℓνb, where ℓ=e, μ, or τ. 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 tt̅ acceptance, particularly for the case in which one W decays as W→τν. 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 subsamples, and a combined cross section is calculated by maximizing a likelihood. The result is σtt̅ =9.6±1.2(stat)-0.5+0.6(sys)±0.6(lum)  pb, assuming a branching ratio of BR(W→ℓν)=10.8% and a top mass of mt=175  GeV/c2.
Beskrivning: 43 pages, 22 figures; Revised version for resubmission to Phys. Rev. D
Subject: hep-ex
114 Physical sciences
Referentgranskad: Ja
Användningsbegränsning: restrictedAccess


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