Measurements of the Top Quark Pair Production Cross Section in Lepton + Jets Final States Using a Topological Multivariate Technique as Well as Lifetime B-Tagging InProton - Anti-proton Collisions at S**(1/2)
Measurements of the Top Quark Pair Production Cross Section in Lepton + Jets Final States Using a Topological Multivariate Technique as Well as Lifetime B-Tagging InProton - Anti-proton Collisions at S**(1/2)

Author: Tobias F. Golling

Publisher:

Published: 2005

Total Pages: 299

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Two alternative measurements of the t{bar t} production cross section at {radical}s = 1.96 TeV in proton-antiproton collisions in the lepton+jets channel are presented. The t{bar t} production cross section is extracted by combining the kinematic event information in a multivariate discriminant. The measurement yields {sigma}{sub p{bar p} {yields} t{bar t} + x} = 5.13{sub -1.57}{sup +1.76}(stat){sub -1.10}{sup +0.96}(syst) {+-} 0.33 (lumi) pb in the muon+jets channel, using 229.1 pb{sup -1}, and in the combination with the electron+jets channel 226.3 pb{sup -1} {sigma}{sub p{bar p} {yields} t{bar t} + x} = 6.60{sub -1.28}{sup +1.37}(stat){sub -1.11}{sup +1.25}(syst) {+-} 0.43 (lumi) pb. The second measurement presented reconstructs explicitly secondary vertices to d lifetime b-tagging. The measurement combines the muon+jets and the electron+jets channel, using 158.4 pb{sup -1} and 168.8 pb{sup -1}, respectively: {sigma}{sub p{bar p} {yields} t{bar t} + x} = 8.24{sub -1.25}{sup +1.34}(stat){sub -1.63}{sup +1.89}(syst) {+-} 0.54 (lumi) pb.

Measurement of the Top Quark Pair Production Cross Section and an In-situ B-tagging Efficiency Calibration with ATLAS in Pp Collisions at √s
Measurement of the Top Quark Pair Production Cross Section and an In-situ B-tagging Efficiency Calibration with ATLAS in Pp Collisions at √s

Author: Bin Guo

Publisher:

Published: 2012

Total Pages:

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We present a measurement of the top anti-top quark (ttbar)production cross section in the dilepton final states from proton-proton collisions at a center of mass energy at 7 TeV at the LHC. A b-tagging algorithm based on tracks displaced from the event interaction vertex is applied to identify bottom quark jets from top quark decay and reject background events. Given the relatively pure sample of bottom quark jets in ttbar dilepton final states, a new technique to measure in-situ the b-tagging efficiency is introduced that uses the distribution of the number of observed b-tagged jets. We present results with data collected at the ATLAS detector in 2010 with an integrated luminosity of 35 pb-1. The measured ttbar cross section is 176 +22/-21 (stat.) ± 20 (syst.) ± 6 (lum.) pb in the dilepton channel. We will also discuss the future prospects of this measurement.

Top Quark Pair Production Cross Section in the Lepton+jets Channel Using B-tagging at
Top Quark Pair Production Cross Section in the Lepton+jets Channel Using B-tagging at

Author:

Publisher:

Published: 2008

Total Pages: 184

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The top quark pair production cross section measurement in the lepton+jets channel with b-tagging algorithm is described. About 900 pb−1 data collected by the D0 detector at the Fermilab Tevatron are used for this analysis. In this thesis, event selection, background estimation, and cross section calculation are discussed in detail. In addition, calibration of the Luminosity Monitor readout electronics and a new b-tagging algorithm, the SLTNN tagger, are also discussed in this thesis.

Observation of Top Quark Production Using Kinematic Techniques
Observation of Top Quark Production Using Kinematic Techniques

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Publisher:

Published: 2001

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We present analysis results of the top quark production using kinematic techniques in p[bar p] collisions at[radical]s= 1.8 TeV with the Collider Detector at Fermilab (CDF). We analyzed a data sample corresponding to an integrated luminosity of 67 pb[sup[minus]1]. First, we compare the kinematic properties, the second and third leading jet E[sub T] of W+> 3 jet events with expectations for t[bar t] production and its back-ground processes, predominantly direct W+ jet production. The probability that backgrounds fake the excess in the signal region was found to be less than 0.26%. Next, we use a scaler sum of the transverse energies of the lepton, neutrino and jets in W+[ge]4 jet events. This analysis shows t[bar t] events exist significantly in the event sample, and enables us to estimate the top quark mass to be M[sub top]= 180[plus-minus] 12[sub[minus]15][sup+19] GeV/c[sup 2]. Finally, we analyse the dijet invariant mass in the W+[ge]4 jet events. It shows a significant mass peak consistent with a mass peak of W decaying into dijet. From these results and counting experiment, we have confirmed previous evidence reported in 1994 April and observed top quark production.