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Total Pages | : 116 |
Release | : 2005 |
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Download Measurement of the Top - Anti-top Production Cross Section at {u221A}s Book in PDF, ePub and Kindle
We discuss the measurement of the cross section for t$ar{t}$ production in p$ar{p}$ collisions at √s = 1.96 TeV in e+jets final states observed at the D0 experiment at the Fermilab Tevatron. Our result is based on data collected from the June 2002 to September 2003 period of Run II of the p$ar{p}$ Collider. In the Standard Model, the top quark is expected to decay mainly into a W boson and a b quark. The W boson can decay subsequently into a lepton and its neutrino or a q$ar{q}$ quark-antiquark pair. In this thesis, we focus on the e+ ve or e- $ar{v}$e decays of one of the W bosons and the q$ar{q}$ decays of the other W boson in t$ar{t}$ final states. The b, q and q' quarks appear as jets of particles in the detector, thereby defining the e+jets final state. We present two methods used for performing this measurement. The first method is based on a Random Grid Search (RGS) that minimizes the uncertainty on the extracted cross section. The variables used in the search take advantage of differences between expected background and signal processes to obtain the yield of t$ar{t}$ events. The second method uses a Neural Network (NN) procedure that discriminates signal from background through the application of a NN trained on simulated t$ar{t}$ signal and W+jets background events. The preliminary results presented in this thesis for inclusive t$ar{t}$ production are ? p$ar{p}$ → t$ar{t}$ + x of 7.9$+2.6top{-2.4}$(stat) $+2.2top{-2.3}$(syst) ± 0.5 (L) pb for the NN analysis, where the uncertainties correspond to contributions from statistical and systematic sources and from the uncertainty on luminosity. Our measurements are consistent with each other, and are within error of the value of 6.77 ± 0.42 pb expected in the Standard Model.
Author | : Joseph Francis Kozminski |
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Total Pages | : 218 |
Release | : 2005 |
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Download Measurements of the Top - Anti-top Production Cross Section at S**(1/2) Book in PDF, ePub and Kindle
The first measurement of the top-antitop production cross section in proton-antiproton collisions at {radical}s = 1.96 TeV using 243 pb{sup -1} of data collected with the D0 detector at Fermilab is presented. In this analysis, only the dielectron final state is considered. Five events are observed, and 0.93 background events are expected. The measured cross section, after accounting for the expected branching ratio to the dielectron channel, is {sigma}{sub t{bar t}} = 14.9{sub -7.0}{sup +9.4}(stat){sub -1.8}{sup +2.5}(syst) {+-} 1.0 (lumi) pb, which agrees with the predicted cross section for top quarks with a mass of 175 GeV. In addition, a first-pass at a measurement of the top mass using the neutrino-weighting method is presented. This measurement is also performed in the dielectron channel using the five events observed in the cross section measurement.
Author | : DooKee Cho |
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Total Pages | : 116 |
Release | : 2005 |
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Download Measurement of the Top - Anti-top Production Cross Section at S**(/1/2) Book in PDF, ePub and Kindle
We discuss the measurement of the cross section for t{bar t} production in p{bar p} collisions at {radical}s = 1.96 TeV in e+jets final states observed at the D0 experiment at the Fermilab Tevatron. Our result is based on data collected from the June 2002 to September 2003 period of Run II of the p{bar p} Collider. In the Standard Model, the top quark is expected to decay mainly into a W boson and a b quark. The W boson can decay subsequently into a lepton and its neutrino or a q{bar q} quark-antiquark pair. In this thesis, we focus on the e{sup +} {nu}{sub e} or e{sup -} {bar {nu}}{sub e} decays of one of the W bosons and the q{bar q} decays of the other W boson in t{bar t} final states. The b, q and q' quarks appear as jets of particles in the detector, thereby defining the e+jets final state. We present two methods used for performing this measurement. The first method is based on a Random Grid Search (RGS) that minimizes the uncertainty on the extracted cross section. The variables used in the search take advantage of differences between expected background and signal processes to obtain the yield of t{bar t} events. The second method uses a Neural Network (NN) procedure that discriminates signal from background through the application of a NN trained on simulated t{bar t} signal and W+jets background events. The preliminary results presented in this thesis for inclusive t{bar t} production are {sigma}{sub p{bar p} {yields} t{bar t} + x} of 7.9{sub -2.4}{sup +2.6}(stat) {sub -2.3}{sup +2.2}(syst) {+-} 0.5 (L) pb for the NN analysis, where the uncertainties correspond to contributions from statistical and systematic sources and from the uncertainty on luminosity. Our measurements are consistent with each other, and are within error of the value of 6.77 {+-} 0.42 pb expected in the Standard Model.
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Total Pages | : |
Release | : 2006 |
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Download Measurements of the Top - Anti-top Production Cross Section at S**(1/2) Book in PDF, ePub and Kindle
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Total Pages | : 39 |
Release | : 2011 |
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Download Measurement of the Top-antitop Production Cross Section in Pp Collisions at Sqrt(s) Book in PDF, ePub and Kindle
A measurement of the top-antitop production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the top-antitop signal from W+jets and QCD multijet background events. The measured cross section is 173 + 39 - 32 (stat. + syst.) pb, consistent with standard model expectations.
Author | : Jan Kieseler |
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Total Pages | : 85 |
Release | : 2012 |
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Download Measurement of the Top-antitop and Z0-boson Production Cross Sections and Their Ratio in the Dileptonic Decay Channels at S Book in PDF, ePub and Kindle
Author | : Danilo Enoque Ferreira de Lima |
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Total Pages | : 0 |
Release | : 2014 |
Genre | : Large Hadron Collider (France and Switzerland) |
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Download Top-antitop Cross Section Measurement as a Function of the Jet Multiplicity in the Final State and Beyond the Standard Model Top-antitop Resonances Search at the ATLAS Detector at CERN Book in PDF, ePub and Kindle
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Total Pages | : 17 |
Release | : 2010 |
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Download Measurement of the $t\bar{t}$ Production Cross Section with an in Situ Calibration of $b$-jet Identification Efficiency Book in PDF, ePub and Kindle
A measurement of the top-quark pair-production cross section in p{bar p} collisions at √s = 1.96 TeV using data corresponding to an integrated luminosity of 1.12 fb−1 collected with the Collider Detector at Fermilab is presented. Decays of top-quark pairs into the final states e[nu] + jets and [mu][nu] + jets are selected, and the cross section and the b-jet identification efficiency are determined using a new measurement technique which requires that the measured cross sections with exactly one and multiple identified b-quarks from the top-quark decays agree. Assuming a top-quark mass of 175 GeV/c2, a cross section of 8.5 ± 0.6(stat.) ± 0.7(syst.) pb is measured.
Author | : Salvatore Rocco Rappoccio |
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Total Pages | : 377 |
Release | : 2005 |
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Download Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**(1/2) Book in PDF, ePub and Kindle
We present the measurement of the t{bar t} cross section in the lepton plus jets channel with {ge} 1 and {ge} 2 secondary vertex tags. We use the scalar sum of transverse energies of the event (H{sub T}) to discriminate t{bar t} from the other backgrounds. We also use the transverse mass of the leptonic W-boson (M{sub T}{sup W}) 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 {sigma} {sub {ge}1} = 8.7{sub -0.9}{sup +0.9}(stat){sub -0.9}{sup +1.2}(sys) pb for the {ge}1 tag cross section, and {sigma}{sub {ge}2} = 8.7{sub -1.6}{sup +1.8}(stat){sub -1.3}{sup +1.9}(sys) pb for the {ge}2 tag cross section. The authors also present a measurement of the t{bar t} cross section by fitting the N{sub jet} spectrum. They combine the =1 and {ge}2 tag cross sections to obtain {sigma}{sub t{bar t}} = 8.9{sub -0.9}{sup +0.9}(stat){sub -1.3}{sup +1.4}(syst)pb.
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Total Pages | : 21 |
Release | : 2014 |
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Download Measurement of the $t\bar{t}$ Production Cross Section in Pp Collisions at $\sqrt{s}$ Book in PDF, ePub and Kindle
The top-quark pair production cross section is measured in final states with one electron or muon and one hadronically decaying [tau] lepton from the process $t\bar{t}$ to (l[nu]l) ([tau][nu][tau]) $b\bar{b}$, where l = e, [mu]. The data sample corresponds to an integrated luminosity of 19.6 fb-1 collected with the CMS detector in proton-proton collisions at $\sqrt{s}$ =8 TeV. The measured cross section [sigma]$t\bar{t}$ = 257 ± 3 (stat) ± 24 (syst) ± 7 (lumi) pb, assuming a top-quark mass of 172.5 GeV, is consistent with the standard model prediction.