Measurement of the Top Quark Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection and Identified B-jets
Measurement of the Top Quark Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection and Identified B-jets

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Published: 2004

Total Pages:

ISBN-13:

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Using 1.0 fb^{-1} of data collected by the Collider Detector at Fermilab (CDF) from Run II of the Fermilab Tevatron, we measure the top-antitop production cross-section in events with two leptons, significant missing transverse energy, and at least jets, at least one of which is identified as a b-jet. As the Run II dataset grows, more stringent tests of Standard Model predictions for the top quark sector are becoming possible. The dilepton channel, where both top quarks decay t-> W b ->l nu b, is of particular interest due to its high purity. Use of an isolated track as the second lepton significantly increases the dilepton acceptance, at the price of some increase in background, particularly from W + jets events where one of the jets is identified as a lepton. To control the increase in background we add to the event selection the requirement that at least one of the jets be identified as a b-jet, reducing the background contribution from all sources. Assuming a branching ratio of BR(W->l nu) = 10.8% and a top mass of m_top = 175 GeV/c^{2} the measured cross-section is sigma = (10.5 +/- 1.8 stat. +/- 0.8 syst. +/- 0.6 lumi.) pb.

Measurement of the Top Quark Pair Production Cross-Section in the Dilepton Channel Using Lepton Plus Track Selection and Identified B-jets
Measurement of the Top Quark Pair Production Cross-Section in the Dilepton Channel Using Lepton Plus Track Selection and Identified B-jets

Author: Teresa Spreitzer

Publisher:

Published: 2008

Total Pages: 282

ISBN-13: 9780494713709

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Using 1.0 fb-1 of data collected by the Collider Detector at Fermilab (CDF) from Run II of the Fermilab Tevatron, we measure the tt ̄ production cross-section in events with two leptons, significant missing transverse energy, and ≥ 2 jets, at least one of which is identified as a b-jet. As the Run II dataset grows, more stringent tests of Standard Model predictions for the top quark sector are becoming possible. The dilepton channel, where both top quarks decay t → Wb → ℓvb, is of particular interest due to its high purity. Use of an isolated Crack as the second lepton significantly increases the dilepton acceptance, at the price of some increase in background, particularly from W + jets events where one of the jets is identified as a lepton. To control the increase in background we add to the event selection the requirement that at least one of the jets be identified as a b-jet, reducing the background contribution from all sources. Assuming a branching ratio of BR(W → ℓ v) = 10.8 % and a top mass of mt = 175 GeV/c2 , the measured cross-section is sigma(pp → tt) = 10.5 +/- 1.8 (stat.) +/- 0.8 (syst. ) +/- 0.6 (lumi.) pb.

A Measurement of the Top Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection
A Measurement of the Top Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection

Author:

Publisher:

Published: 2007

Total Pages: 214

ISBN-13:

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Using 1.1 fb−1 of data collected by the Collider Detector at Fermilab (CDF) from Run II of the Fermilab Tevatron, they measure the t{bar t} production cross section in events with two leptons, significant missing transverse energy, and ≥ 2 jets. As the Run II dataset grows, more stringent tests of Standard Model predictions for the top quark sector are becoming possible. The dilepton channel, where both top quarks decay t → Wb → l[nu]b, is of particular interest due to its high purity even in the absence of a b jet 'tagging' requirement. Use of an isolated track as the second lepton significant increases the dilepton acceptance, at the price of some increase in background, particular from W + jets events where one of the jets is identified as a lepton. With the amount of data available, it has been possible to improve the estimate of the contribution from that background, reflected in a reduced systematic uncertainty. Assuming a branching ratio of BR(W → l[nu]) = 10.8% and a top mass of m{sub t} = 175 GeV/c2, the measured cross-section is [sigma](p{bar p} → t{bar t}) = 8.3 ± 1.3(stat.) ± 0.7(syst.) ± 0.5(lumi.) pb. The result is consistent with the Standard Model prediction of 6.7{sub -0.9}{sup +0.7} pb and represents a significant improvement in precision over previous results using this selection.

A Measurement of the Top Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection
A Measurement of the Top Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection

Author: Corrinne Mills

Publisher: ProQuest

Published: 2007

Total Pages: 388

ISBN-13: 9780549152866

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Using 1.1 fb-1 of data collected by the Collider Detector at Fermilab (CDF) from Run II of the Fermilab Tevatron, we measure the tt production cross section in events with two leptons, significant missing transverse energy, and & ge;2 jets. As the Run II dataset grows, more stringent tests of Standard Model predictions for the top quark sector are becoming possible. The dilepton channel, where both top quarks decay t & rarr; Wb & rarr; & ell;nu b, is of particular interest due to its high purity even in the absence of a b jet "tagging" requirement. Use of an isolated track as the second lepton significantly increases the dilepton acceptance, at the price of some increase in background, particularly from W + jets events where one of the jets is identified as a lepton. With the amount of data available, it has been possible to improve the estimate of the contribution from that background, reflected in a reduced systematic uncertainty. Assuming a branching ratio of BR(W & rarr; & ell;nu) = 10.8% and a top mass of mt = 175 GeV/ c2, the measured cross-section is sigma(pp & rarr; tt) + 8.3 +/- 1.3(stat.) +/- 0.7(syst.) +/- 0.5(lumi.) pb. The result is consistent with the Standard Model prediction of 6.7+0.7-0.9 pb and represents a significant improvement in precision over previous results using this selection.

Measurement of the Top Quark Pair Production Cross Section in the Dilepton Channel Using Lepton+track Selection
Measurement of the Top Quark Pair Production Cross Section in the Dilepton Channel Using Lepton+track Selection

Author:

Publisher:

Published: 2008

Total Pages: 137

ISBN-13:

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The production cross section for t{bar t} pairs decaying into two lepton final states was measured using data from the D0 detector at Fermilab. The measurement was made using a lepton+track selection, where one lepton is fully identified and the second lepton is observed as an isolated track. This analysis is designed to complement similar studies using two fully identified leptons [1]. The cross section for the lepton+track selection was found to be [sigma] = 5.2{sub -1.4}{sup +1.6}(stat){sub -0.8}{sup +0.9}(syst) ± 0.3(lumi) pb. The combined cross section using both the lepton+track data and the data from the electron+electron, electron+muon, and muon+muon samples is: [sigma] = 6.4{sub -0.9}{sup +0.9}(stat){sub -0.7}{sup +0.8}(syst) ± 0.4(lumi) pb.

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

ISBN-13:

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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.

Top Quark Physics at Hadron Colliders
Top Quark Physics at Hadron Colliders

Author: Arnulf Quadt

Publisher: Springer Science & Business Media

Published: 2007-08-16

Total Pages: 166

ISBN-13: 3540710604

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This will be a required acquisition text for academic libraries. More than ten years after its discovery, still relatively little is known about the top quark, the heaviest known elementary particle. This extensive survey summarizes and reviews top-quark physics based on the precision measurements at the Fermilab Tevatron Collider, as well as examining in detail the sensitivity of these experiments to new physics. Finally, the author provides an overview of top quark physics at the Large Hadron Collider.

Measurements of the Top Quark Pair Production Cross Section and Branching Ratio to a W-boson and Bottom Quark Using the Semi-leptonic and Dilepton Final States with the ATLAS Detector at the LHC
Measurements of the Top Quark Pair Production Cross Section and Branching Ratio to a W-boson and Bottom Quark Using the Semi-leptonic and Dilepton Final States with the ATLAS Detector at the LHC

Author: Robert E. Calkins

Publisher:

Published: 2012

Total Pages: 241

ISBN-13: 9781267906960

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Abstract : In the Standard Model, the top quark plays a unique role as the heaviest known fundamental particle and as a quark that decays before it is able to hadronize. Top quarks are expected to decay to a W-boson and a b-quark nearly 100% of the time. If the branching ratio of t → Wb is lower than one, the distribution of the number of b-tagged jets will shift to lower multiplicities. A simultaneous likelihood fit to the number of b-tagged jets distributions in the lepton+jets and dilepton channels is performed on 4.7 fb−1 of data collected by the ATLAS detector to extract both the branching ratio and the tt ̄ cross section. The branching ratio of t → Wb, R, is measured to be 1.06±0.11, which is consistent with the Standard Model value. This is the first measurement of the t → Wb branching ratio performed with the ATLAS detector using both the lepton+jets and dilepton channels at the LHC. The tt ̄ cross section is measured to be [special characters omitted] pb, which agrees with NNLO predictions.