Measurement of the Top - Anti-top Production Cross Section at S**(/1/2)

Measurement of the Top - Anti-top Production Cross Section at S**(/1/2)
Author: DooKee Cho
Publisher:
Total Pages: 116
Release: 2005
Genre:
ISBN:

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.

Measurements of the Top - Anti-top Production Cross Section at S**(1/2)

Measurements of the Top - Anti-top Production Cross Section at S**(1/2)
Author: Joseph Francis Kozminski
Publisher:
Total Pages: 218
Release: 2005
Genre:
ISBN:

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.

Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**1/2

Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**1/2
Author:
Publisher:
Total Pages: 24
Release: 2007
Genre:
ISBN:

We present a measurement of the top quark pair production cross section in p{bar p} collisions at √s = 1.96 TeV utilizing 425 pb−1 of data collected with the D0 detector at the Fermilab Tevatron Collider. We consider the final state of the top quark pair containing one high-p{sub T} electron or muon and at least four jets. We exploit specific kinematic features of t{bar t} events to extract the cross section. For a top quark mass of 175 GeV, we measure [sigma]{sub t{bar t}} = 6.4{sub -1.2}{sup +1.3}(stat) ± 0.7(syst) ± 0.4(lum)pb, in good agreement with the standard model prediction.

Measurement of the P Anti-p ---] T Anti-t Production Cross- Section and the Top Quark Mass at S**1/2

Measurement of the P Anti-p ---] T Anti-t Production Cross- Section and the Top Quark Mass at S**1/2
Author:
Publisher:
Total Pages: 29
Release: 2007
Genre:
ISBN:

We report the measurements of the t{bar t} production cross section and of the top quark mass using 1.02 fb−1 of p{bar p} data collected with the CDF II detector at the Fermilab Tevatron. We select events with six or more jets on which a number of kinematical requirements are imposed by means of a neural network algorithm. At least one of these jets must be identified as initiated by a b-quark candidate by the reconstruction of a secondary vertex. The cross section is measured to be [sigma]{sub t{bar t}} = 8.3 ± 1.0(stat.){sup +2.0}{sub -1.5}(syst.) ± 0.5(lumi.) pb, which is consistent with the standard model prediction. The top quark mass of 174.0 ± 2.2(stat.)±4.8(syst.) GeV/c2 is derived from a likelihood fit incorporating reconstructed mass distributions representative of signal and background.

Measurement of the P Anti-p --] T Anti-t Production Cross Section at S**1/2

Measurement of the P Anti-p --] T Anti-t Production Cross Section at S**1/2
Author:
Publisher:
Total Pages: 10
Release: 2006
Genre:
ISBN:

A measurement of the top quark pair production cross section in proton anti-proton collisions at an interaction energy of √s = 1.96 TeV is presented. This analysis uses 405 pb−1 of data collected with the D0 detector at the Fermilab Tevatron Collider. Fully hadronic t{bar t} decays with final states of six or more jets are separated from the multijet background using secondary vertex tagging and a neural network. The t{bar t} cross section is measured as [sigma]{sub t{bar t}} = 4.5{sub -1.9}{sup +2.0}(stat){sub -1.1}{sup +1.4}(syst) ± 0.3(lumi) pb for a top quark mass of m{sub t} = 175 GeV/c2.

Measurement of the Top-antitop Production Cross Section in Pp Collisions at Sqrt(s)

Measurement of the Top-antitop Production Cross Section in Pp Collisions at Sqrt(s)
Author:
Publisher:
Total Pages: 39
Release: 2011
Genre:
ISBN:

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.

Улов

Улов
Author:
Publisher:
Total Pages: 227
Release: 2000
Genre: Russian literature
ISBN:

Measurement of the Top Quark Pair Production Cross Section in P Anti-p Collisions at S**(1/2)

Measurement of the Top Quark Pair Production Cross Section in P Anti-p Collisions at S**(1/2)
Author: Gustavo J. Otero y Garzon
Publisher:
Total Pages: 378
Release: 2006
Genre:
ISBN:

The subject of this thesis is the measurement of the rate at which a top-antitop quark pair is produced in pp collisions at a center of mass energy of ps = 1:96 TeV. The data are collected with the D detector, a multi-purpose detector operating at the Fermilab Tevatron collider during Run II. A measurement of the top quark pair (t$\bar{t}$) production cross section ( [sigma]t$\bar{t}$) in p$\bar{p}$ collisions at a center of mass energy of 1.96 TeV is presented. The measurement is based on data recorded by the D0 Detector at the Fermilab Tevatron Collider, and preselected in the e+jets (366 pb-1) and [mu]+jets (363 pb-1) channels. The cross section is extracted by applying a lifetime-tagging technique to the data, and yields [sigma]t$\bar{t}$ = 6.96$+1.07\atop{-0.98}$(stat + syst) ± 0.45(lumi) pb; for a top quark mass mt =175 GeV, in good agreement with the Standard Model prediction.

Measurement of the Top - Anti-top Production Cross Section at {u221A}s

Measurement of the Top - Anti-top Production Cross Section at {u221A}s
Author:
Publisher:
Total Pages: 116
Release: 2005
Genre:
ISBN:

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.