Measurement Of The T Bar T Production Cross Section In P Bar P Collisions At U221a S
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Measurement of the T$\bar{t}$ Production Cross Section in P$\bar{p}$ Collisions at {u221A}s
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.
A Measurement of the Production Cross Section of T$\bar{t}$ in P$\bar{p}$ Collisions at {u221A}s
A measurement of the t$\bar{t}$ pair production cross section is presented using 162 pb -1 of data collected by the CDF experiment during Run II at the Tevatron. t$\bar{t}$} events in the lepton+jets channel are isolated by identifying electrons and muons, reconstructing jets and transverse missing energy, and identifying b jets with a secondary vertex tagging algorithm. The efficiency of the algorithm is measured in a control sample using a novel technique that is less dependent on the simulation. For a top quark mass of 175 GeV/c2 , a cross section of ?t$\bar{t}$ = 5.6$+1.2\atop{-1.1}$(stat.)$+0.9\atop{-0.6}$(syst.)pb is measured.
Measurement of the T-tbar Production Cross Section in P-pbar Collisions at {u221A}s
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$ar{t}$.