Download or read book Measurement of the T Anti t Production Cross Section in P Anti p Collisions at u221A s written by and published by . This book was released on 2004 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: The direct observation of the top quark was first achieved at the Tevatron proton anti-proton collider at Fermilab. This discovery completed the third generation quark sector where the top quark is expected to accompany the bottom quark in the weak isospin doublet. This dissertation discusses the experimental verification of the production cross section as predicted by the Standard Model. A measurement of the t$ar{t}$ production cross section using 107.9 pb-1 of p$ar{p}$ collisions at √s = 1.96 TeV collected with the Collider Detector at Fermilab between March of 2003 and June of 2003 is presented. The measurement focuses on the t$ar{t}$ production in the ''lepton plus jets'' final state in which one of the W bosons from the t$ar{t}$ decay subsequently decays leptonically to an electron or a muon, and the other decays hadronically. The B-tagging technique which utilizes the precision silicon detector tracking is used to enhance the signal for t$ar{t}$ events relative to the background through identification of the bottom quark from its measurable lifetime. The t$ar{t}$ production cross section is measured to be ?t$ar{t}$ = 4.5 ± 1.4(stat) ± 0.8(sys) pb.

Download or read book A Measurement of the T Anti t Production Cross section in Proton Anti proton Collisions at u221A s written by and published by . This book was released on 2004 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: A preliminary measurement of the t$ar{t}$ production cross section at √s = 1.96 TeV is presented. The ?-plus-jets final state is analyzed in a data sample of 94 pb-1 and a total of 14 events are selected with a background expectation of 11.7 ± 1.9 events. The measurement yields: ?p$ar{p}$ → t$ar{t}$ + X} = 2.4$+4.2top{-3.5}$(stat.)$+2.5top{-2.6}$(syst.) ± 0.3(lumi.) pb. The analysis, being part of a larger effort to re-observe the top quark in Tevatron Run II data and to measure the production cross section, is combined with results from all available analyses channels. The combined result yields: ? p$ar{p}$ → t$ar{t}$ + X = 8.1$+2.2top{-2.0}$(stat.)$+1.6top{-1.4}$(syst.) ± 0.8(lumi.) pb.

Download or read book T Anti t Production Cross Section Measurement Using Soft Electron Tagging in P Anti p Collisions at u221A s written by and published by . This book was released on 2008 with total page 261 pages. Available in PDF, EPUB and Kindle. Book excerpt: We measure the production cross section of t$ar{t}$ events in p$ar{p}$ collisions at √s = 1.96 TeV. The data was collected by the CDF experiment in Run 2 of the Tevatron accelerator at the Fermi National Accelerator Laboratory between 2002 and 2007. 1.7 fb-1 of data was recorded during this time period. We reconstruct t$ar{t}$ events in the lepton+jets channel, whereby one W boson - resulting from the decay of the top quark pairs - decays leptonically and the other hadronically. The dominant background to this process is the production of W bosons in association with multiple jets. To distinguish t$ar{t}$ from background, we identify soft electrons from the semileptonic decay of heavy flavor jets produced in t$ar{t}$ events. We measure a cross section of ?$ar{p}$ = 7.8 ± 2.4(stat) ± 1.6(syst) ± 0.5(lumi).

Download or read book Measurement of the Top Anti top Production Cross Section at u221A s written by and published by . This book was released on 2005 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Measurement of the T Anti t Production Cross Section in P Anti p Collisions at S 1 2 written by Lucio Cerrito and published by . This book was released on 2005 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present two measurements of the t{bar t} production cross section in collisions of protons and antiprotons at {radical}s = 196 TeV. We analyze a dataset of 310 {+-} 20 pb{sup -1} collected with the CDF 2 detector. In the first measurement, we select events with six to eight jets, at least one of which having a displaced secondary vertex, little or no missing transverse energy and optimized kinematical criteria consistent with the t{bar t} all-hadronic decay channel. In the second measurement, we select events with four or more jets, at least one of which having a displaced secondary vertex, high missing transverse energy, and optimized kinematical criteria consistent with the decay of t{bar t} to {tau}+jets. The averaged t{bar t} production cross section, determined from six different measurements using the CDF 2 detector in the dilepton, lepton+jets and all-hadronic decay channels, is also calculated to be {sigma}{sub t{bar t}} = 7.1 {+-} 0.6(stat) {+-} 0.7(syst) {+-} 0.4(lumi) pb, in agreement with the prediction of the standard model.

Download or read book A Measurement of the T Anti t Production Cross Section in P Anti p Collisions at S 1 2 written by and published by . This book was released on 2008 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: I present a measurement of the t{bar 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{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 248 candidate events and an expected background of 86.8 ± 5.6 events, I measure a production cross section of 8.7 ± 1.1{sub -0.8}{sup +0.9} ± 0.6 pb, in agreement with the Standard Model.

Download or read book Measurement of the T Anti t Production Cross Section in P Anti p Collisions at S 1 2 written by and published by . This book was released on 2005 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the top quark pair (t{bar t}) production cross section ([sigma]{sub t{bar t}}) in p{bar p} collisions at √s = 1.96 TeV using 230 pb−1 of data collected by the D0 experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the t{bar t} purity of the selected sample. For a top quark mass of 175 GeV, we measure [sigma]{sub t{bar t}} = 8.6{sub -1.5}{sup +1.6}(stat. + syst.) ± 0.6 (lumi.) pb, in agreement with the standard model expectation.

Download or read book Measurement of the T Anti t Production Cross Section in P Anti p Collisions at S 1 2 written by Salvatore Rocco Rappoccio and published by . This book was released on 2005 with total page 377 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Measurement of the T Anti t Production Cross Section in P Anti p Collisions at S written by and published by . This book was released on 2007 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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?{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.

Download or read book Measurement of the T Anti t Production Cross Section in P pbar Collisions at S 1 2 written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract Not Provided.

Download or read book Measurement of the Cross Section for T Anti t Production in P Anti p Collisions Using the Kinematics of Lepton Jets Events written by and published by . This book was released on 2005 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present a measurement of the top pair production cross section in p{bar p} collisions at √s = 1.96 TeV. We collect a data sample with an integrated luminosity of 194 ± 11 pb−1 with the CDF II detector at the Fermilab Tevatron. We use an artificial neural network technique to discriminate between top pair production and background processes in a sample of 519 lepton + jets events, which have one isolated energetic charged lepton, large missing transverse energy and at least three energetic jets. We measure the top pair production cross section to be [sigma]{sub t{bar t}} = 6.6 ± 1.1 ± 1.5 pb, where the first uncertainty is statistical and the second is systematic.

Download or read book A Measurement of the T Anti t Cross Section in P Anti p Collisions at S written by and published by . This book was released on 2009 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper reports a measurement of the cross section for the pair production of top quarks in p{bar p} collisions at √s = 1.96 TeV at the Fermilab Tevatron. The data was collected from the CDF II detector in a set of runs with a total integrated luminosity of 1.1 fb−1. The cross section is measured in the dilepton channel, the subset of t{bar t} events in which both top quarks decay through t → Wb → l?b, where l = e,?, or?. The lepton pair is reconstructed as one identified electron or muon and one isolated track. The use of an isolated track to identify the second lepton increases the t{bar t} acceptance, particularly for the case in which one W decays as W →??. The purity of the sample may be further improved at the cost of a reduction in the number of signal events, by requiring an identified b-jet. They present the results of measurements performed with and without the request of an identified b-jet. the former is the first published CDF result for which a b-jet requirement is added to the dilepton selection. In the CDF data there are 129 pretag lepton + track candidate events, of which 69 are tagged. With the tagging information, the sample is divided into tagged and untagged sub-samples, and a combined cross section is calculated by maximizing a likelihood. The result is?{sub t{bar t}} = 9.6 ± 1.2(stat.){sub -0.5}{sup +0.6}(sys.) ± 0.6(lum.) pb, assuming a branching ratio of BR(W → l?) = 10.8% and a top mass of m{sub t} = 175 GeV/c2.

Download or read book A Measurement of the T Anti t Cross Section in P Anti p Collisions at S 1 2 written by and published by . This book was released on 2009 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper reports a measurement of the cross section for the pair production of top quarks in p{bar p} collisions at √s = 1.96 TeV at the Fermilab Tevatron. The data was collected from the CDF II detector in a set of runs with a total integrated luminosity of 1.1 fb−1. The cross section is measured in the dilepton channel, the subset of t{bar t} events in which both top quarks decay through t → Wb → l[nu]b, where l = e, [mu], or [tau]. The lepton pair is reconstructed as one identified electron or muon and one isolated track. The use of an isolated track to identify the second lepton increases the t{bar t} acceptance, particularly for the case in which one W decays as W → [tau][nu]. The purity of the sample may be further improved at the cost of a reduction in the number of signal events, by requiring an identified b-jet. They present the results of measurements performed with and without the request of an identified b-jet. the former is the first published CDF result for which a b-jet requirement is added to the dilepton selection. In the CDF data there are 129 pretag lepton + track candidate events, of which 69 are tagged. With the tagging information, the sample is divided into tagged and untagged sub-samples, and a combined cross section is calculated by maximizing a likelihood. The result is [sigma]{sub t{bar t}} = 9.6 ± 1.2(stat.){sub -0.5}{sup +0.6}(sys.) ± 0.6(lum.) pb, assuming a branching ratio of BR(W → l[nu]) = 10.8% and a top mass of m{sub t} = 175 GeV/c2.

Download or read book Measurement of the T Anti t Production Cross Section in P Anti p Collistions at S 1 2 written by and published by . This book was released on 2005 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present a measurement of the top quark pair (t{bar t}) production cross section in p{bar p} collisions at √s = 1.96 TeV using events with two charged leptons in the final state. This analysis utilizes an integrated luminosity of 224-243 pb−1 collected with the D0 detector at the Fermilab Tevatron Collider. They observe 13 events in the e+e−, e? and ?+ ?− channels with an expected background of 3.2 ± 0.7 events. For a top quark mass of 175 GeV, we measure a t{bar t} production cross section of ?{sub t{bar t}} = 8.6{sub -2.7}{sup +3.2}(stat) ± 1.1(syst) ± 0.6(lumi) pb, consistent with the standard model prediction.

Download or read book Measurement of the T Anti t Production Cross Section in P Anti p Collisions at S 1 2 written by Heather Lynn Ray and published by . This book was released on 2004 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: The direct observation of the top quark was first achieved at the Tevatron proton anti-proton collider at Fermilab. This discovery completed the third generation quark sector where the top quark is expected to accompany the bottom quark in the weak isospin doublet. This dissertation discusses the experimental verification of the production cross section as predicted by the Standard Model. A measurement of the t{bar t} production cross section using 107.9 pb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV collected with the Collider Detector at Fermilab between March of 2003 and June of 2003 is presented. The measurement focuses on the t{bar t} production in the ''lepton plus jets'' final state in which one of the W bosons from the t{bar t} decay subsequently decays leptonically to an electron or a muon, and the other decays hadronically. The B-tagging technique which utilizes the precision silicon detector tracking is used to enhance the signal for t{bar t} events relative to the background through identification of the bottom quark from its measurable lifetime. The t{bar t} production cross section is measured to be {sigma}{sub t{bar t}} = 4.5 {+-} 1.4(stat) {+-} 0.8(sys) pb.

Download or read book A Measurement of T anti T Production Cross Section in P anti P Collisions At radical written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present the results of a new measurement of the t[anti t] production cross section using e[mu] channel in p[anti p] collisions at[radical]s= 1.8 TeV. This study corresponds to an integrated luminosity of 108.3[+-] 5.7 pb[sup[minus]1] acquired by the D0 detector during the Fermilab Tevatron Collider Run 1 (1992--1996). By using neural network techniques instead of the conventional analysis methods, the authors show that the signal acceptance can be increased by 10% (for m[sub t]= 172 GeV/c[sup 2]) while the background remains constant. Four e[mu] events are observed in data with an estimated background of 0.22[+-] 0.14 corresponding to a t[anti t] production cross section of 9.75[+-] 5.53 pb.

Download or read book Measurement of the P Anti p T Anti t Production Cross Section at S written by and published by . This book was released on 2006 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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?{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.