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Measurement Of The T Tbar Production Cross Section In P Pbar Collisions At U221a S

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Measurement Of The T Tbar Production Cross Section In P Pbar Collisions At U221a S

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language : en
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Release Date : 2006

Measurement Of The T Tbar Production Cross Section In P Pbar Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.

The top quark is the most massive fundamental particle observed so far, and the study of its properties is interesting for several reasons ranging from its possible special role in electroweak symmetry breaking to its sensitivity to physics beyond the standard model (SM). In particular, the measurement of the top quark pair production cross section ?t$ar{t}$ is of interest as a test of QCD predictions. Recent QCD calculations done with perturbation theory to next-to-leading order predict ?t$ar{t}$ with an uncertainty of less than 15%, which motivate measurements of comparable precision. In this thesis, the author reports a measurement of the cross section for pair production of top quarks in the lepton+jets channel in 318 pb-1 of p$ar{p}$ collision data at √s = 1.96 TeV. The data were recorded between March 2002 and September 2004, during Run II of the Tevatron, by the CDF II detector, a general purpose detector which combines charged particle trackers, sampling calorimeters, and muon detectors. processes in which a W boson is produced in association with several jets with large transverse momentum can be misidentified at t$ar{t}$, since they have the same signature. In order to separate the t$ar{t}$ events from this background, they develop a method to tag b-jets based on tracking information from the silicon detector. The main event selection requires at least one tight (more restrictive) b tag in the event. As a cross check, they also measure the cross section using events with a loose (less restrictive) b tag and events which have at least two tight or at least two loose b tags. Background contributions from heavy flavor production processes, such as Wb$ar{b}$, Wc$ar{c}$ or Wc, misidentified W bosons, electroweak processes, single top production, and mistagged jets are estimated using a combination of Monte Carlo calculations and independent measurements in control data samples. An excess over background in the number of events that contain a lepton, missing energy and three or more jets with at least one b-tag is assumed to be a signal of t$ar{t}$ production and is used to measure the production cross section ?t$ar{t}$.

Measurement Of The Ttbar Production Cross Section In Ppbar Collisions At Sqrt S

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language : en
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Release Date : 2010

Measurement Of The Ttbar Production Cross Section In Ppbar Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.

We present a measurement of the top quark pair production cross section in p{bar p} collisions at √s = 1.96 TeV using a data sample corresponding to 1.7 fb−1 of integrated luminosity collected with the Collider Detector at Fermilab. We reconstruct t{bar t} events in the lepton+jets channel, consisting of e[nu]+jets and [mu][nu]+jets final states. The dominant background is the production of W bosons in association with multiple jets. To suppress this background, we identify electrons from the semileptonic decay of heavy-flavor jets ('soft electron tags'). From a sample of 2196 candidate events, we obtain 120 tagged events with a background expectation of 51 ± 3 events, corresponding to a cross section of [sigma]{sub t{bar t}} = 7.8 ± 2.4 (stat) ± 1.6 (syst) ± 0.5 (lumi) pb. We assume a top-quark mass of 175 GeV/c2. This is the first measurement of the t{bar t} cross section with soft electron tags in Run II of the Tevatron.

Measurement Of The T Bar T Production Cross Section In P Bar P Collisions At U221a S

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language : en
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Release Date : 2005

Measurement Of The T Bar T Production Cross Section In P Bar P Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.

We present the measurement of the t$ar{t}$ cross section in the lepton plus jets channel with ≥ 1 and ≥ 2 secondary vertex tags. We use the scalar sum of transverse energies of the event (HT) to discriminate t{bar t} from the other backgrounds. We also use the transverse mass of the leptonic W-boson (M$Wtop{T}$) to further reduce the Non-W backgrounds. We use a combination of data and Monte Carlo to estimate the backgrounds from electroweak processes, single top, fake leptons, W+ Light Flavor fake tags, and real W+ Heavy Flavor production. We obtain a value of ? ≥1 = 8.7$+0.9top{-0.9}$(stat)$+1.2top{-0.9}$(sys) pb for the ≥1 tag cross section, and ? ≥2 = 8.7$+1.8top{-1.6}$(stat)$+1.9top{-1.3}$(sys) pb for the ≥2 tag cross section. The authors also present a measurement of the t$ar{t}$ cross section by fitting the Njet spectrum. They combine the =1 and ≥2 tag cross sections to obtain ?t$ar{t}$ = 8.9$+0.9top{-0.9}$(stat)$+1.4top{-1.3}$(syst)pb.

Measurement Of The Ttbar Production Cross Section In 2 Fb 1 Of Ppbar Collisions At Sqrt S

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language : en
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Release Date : 2009

Measurement Of The Ttbar Production Cross Section In 2 Fb 1 Of Ppbar Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.

We present a measurement of the t{bar t} production cross section in p{bar p} collisions at (square root)s = 1.96 TeV using events containing a high transverse momentum electron or muon, three or more jets, and missing transverse energy. Events consistent with t{bar t} decay are found by identifying jets containing candidate heavy-flavor semileptonic decays to muons. The measurement uses a CDF Run II data sample corresponding to 2 fb−1 of integrated luminosity. Based on 248 candidate events with three or more jets and an expected background of 79.5 ± 5.3 events, we measure a production cross section of 9.1 ± 1.6 pb.

Measurement Of The T Bar T Production Cross Section In P Bar P Collisions At Sqrt S

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language : en
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Release Date : 2004

Measurement Of The T Bar T Production Cross Section In P Bar P Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.

Measurement Of The Ttbar Production Cross Section In Ppbar Collisions At S

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Author :
language : en
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Release Date : 2005

Measurement Of The Ttbar Production Cross Section In Ppbar Collisions At S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.

We present the measurement of the top quark pair production cross section in p{bar p} collisions at √s = 1.96 TeV using 318 pb−1 of data collected by the CDF detector at the Fermilab Tevatron. We measure the cross section in events with one high transverse momentum electron or muon, large missing transverse energy and three or more jets, where at least one bottom quarks from the top quark decay is identified via a secondary vertex tagging algorithm. The measured t{bar t} cross section is 8.7{sub -0.9}{sup +0.9}(stat){sub -0.9}{sup +1.2}(syst) pb, assuming a top quark mass of 178 GeV. The cross section measurement in the subsample in which both b-quark jets are identified gives 10.1{sub -1.4}{sup +1.6}(stat){sub -1.4}{sup +2.1}(syst) pb. We present one additional measurement of the t{bar t} cross section in the same dataset but without the b-tagging requirement. Top quark events are distinguished from the primary background of W boson production with associated jets using an artificial neural network method with a variety of kinematic quantities. This measurement uses a larger dataset albeit with a smaller t{bar t} fraction. The t{bar t} cross section without b-tagging is measured to be 6.0 ± 0.8(stat) ± 1.0(syst) pb.

Top Physics

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language : en
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Release Date : 2005

Top Physics written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.

We present a measurement of the t{bar t} production cross section using 194 pb−1 of CDF II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes 100% t --> Wb branching fraction. Events consistent with t{bar t} decay are found by identifying jets containing heavy flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 20 candidate events and an expected background of 9.5 " 1.1 events, we measure a production cross section of 5.3 " 3.3{sub -1.0}{sup +1.3} pb, in agreement with the standard model.

Measurement Of The T Bar T Cross Section Using The Dimuon Channel In P Bar P Collisions At U221a S

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language : en
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Release Date : 2004

Measurement Of The T Bar T Cross Section Using The Dimuon Channel In P Bar P Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.

The author has measured the t$ar{t}$ production cross section at √s = 1.96 TeV using data collected by the D0 experiment at Fermilab. The integrated luminosity of the data set is 140 pb-1 and a total of four candidate events are seen, with an expected background of 2.61 events. The measured cross section of ?t$ar{t}$ = 11.1$+22.1top{-9.3}$(stat.)$+4.3top{-4.5}$(sys.) pb is in agreement with a NNLO calculation of 6.77 pb.

Measurement Of The Ttbar Production Cross Section In Ppbar Collisions At S 1 2

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language : en
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Release Date : 2005

Measurement Of The Ttbar Production Cross Section In Ppbar Collisions At S 1 2 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.

A Measurement Of The T Bar T Production Cross Section In P Bar P Collisions At U221a S

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Author :
language : en
Publisher:
Release Date : 2008

A Measurement Of The T Bar T Production Cross Section In P Bar P Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.

I present a measurement of the t$ar{t}$ production cross section at √s = 1.96 TeV using 2034 pb-1 of CDF Run II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes a t → Wb branching fraction of 100 percent. Events consistent with t$ar{t}$ decay are found by identifying jets containing heavy-flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 248 candidate events and an expected background of 86.8 ± 5.6 events, I measure a production cross section of 8.7 ± 1.1$+0.9top{-0.8}$ ± 0.6 pb, in agreement with the Standard Model.

Measurement Of The T Tbar Production Cross Section In P Pbar Collisions At U221a S

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