Download or read book Measurement of the T tbar Production Cross Section in the CDF Detector written by Jose Enrique Palencia Cortezón and published by . This book was released on 2013-11-16 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the T Tbar Cross Section at the Run II Tevatron Using Support Vector Machines written by and published by . This book was released on 2010 with total page 419 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation measures the t{bar t} production cross section at the Run II CDF detector using data from early 2001 through March 2007. The Tevatron at Fermilab is a p{bar p} collider with center of mass energy √s = 1.96 TeV. This data composes a sample with a time-integrated luminosity measured at 2.2 ± 0.1 fb−1. A system of learning machines is developed to recognize t{bar t} events in the 'lepton plus jets' decay channel. Support Vector Machines are described, and their ability to cope with a multi-class discrimination problem is provided. The t{bar t} production cross section is then measured in this framework, and found to be [sigma]{sub t{bar t}} = 7.14 ± 0.25 (stat){sub -0.86}{sup +0.61}(sys) pb.
Download or read book Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S written by and published by . This book was released on 2005 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Measurement of the T tbar Production Cross Section in P pbar Collisions at u221A s written by and published by . This book was released on 2006 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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$ar{t}$.
Download or read book Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S 1 2 written by and published by . This book was released on 2005 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Modern Drawings and Watercolours written by and published by . This book was released on 1967 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the T Tbar Production Cross Section at written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on the results from the analyses of[ital t][ital[anti t]] decays in[ital dilepton] and[ital lepton+jets] modes with[approx]100 pb[sup -1] of[ital p][ital[anti p]] Collider data at[radical]s= 1.8 TeV collected by the D[null] experiment at the Fermilab Tevatron. We have observed 37[ital t][ital[anti t]] candidate events while the estimated background is 13.4[+-] 3.0 events. The[ital t][ital[anti t]] production cross section has been measured to be 5.2[+-] 1.8 pb at a top quark mass of 170 GeV/c[sup 2].
Download or read book Measurement of the Ttbar Production Cross Section in the MET jets Channel at CDF written by and published by . This book was released on 2008 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is focused on an inclusive search of the t{bar t} --> E{sub T} + jets decay channel by means of neural network tools in proton antiproton collisions at (square root)s = 1.96 TeV recorded by the Collider Detector at Fermilab (CDF). At the Tevatron p{bar p} collider top quarks are mainly produced in pairs through quark-antiquark annihilation and gluon-gluon fusion processes; in the Standard Model description, the top quark then decays to a W boson and a b quark almost 100% of the times, so that its decay signatures are classified according to the W decay modes. When only one W decays leptonically, the t{bar t} event typically contains a charged lepton, missing transverse energy due to the presence of a neutrino escaping from the detector, and four high transverse momentum jets, two of which originate from b quarks. In this thesis we describe a t{bar t} production cross section measurement which uses data collected by a 'multijet' trigger, and selects this kind of top decays by requiring a high-P{sub T} neutrino signature and by using an optimized neural network to discriminate top quark pair production from backgrounds. In Chapter 1, a brief review of the Standard Model of particle physics will be discussed, focusing on top quark properties and experimental signatures. In Chapter 2 will be presented an overview of the Tevatron accelerator chain that provides p{bar p} collisions at the center-of-mass energy of (square root)s = 1.96 TeV, and proton and antiproton beams production procedure will be discussed. The CDF detector and its components and subsystems used for the study of p{bar p} collisions provided by the Tevatron will be described in Chapter 3. Chapter 4 will detail the reconstruction procedures used in CDF to detect physical objects exploiting the features of the different detector subsystems. Chapter 5 will provide an overview of the main concepts regarding Artificial Neural Networks, one of the most important tools we will use in the analysis. Chapter 6 will be devoted to the description of the main characteristics of the t{bar t} --> E{sub T} + jets decay channel used to train our neural network to discriminate the top pair production from background processes. We will discuss the event selection method and the technique used for background prediction, that will rely on b-jets identification rate parameterization. Finally, Chapter 7 will provide a description of the final data sample and a detailed discussion of the systematic uncertainties before determining the cross section measurement by means of a likelihood maximization.
Download or read book Top Physics written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Measurement of the Tt bar Production Cross Section in the Dilepton Channel at CDF written by Reda Tafirout and published by . This book was released on 2004 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report a measurement of the t{bar t} production cross section using dilepton events with jets and missing transverse energy in p{bar p}collisions at {radical}s = 1.96 TeV. Using 197 pb{sup -1} of data recorded by the upgraded Collider Detector at Fermilab (CDF II), we use two complementary techniques to select candidate events. The combined result yields a t{bar t} production cross section of 7.0{sub -2.1}{sup +2.4}(stat){sub -1.1}{sup +1.6}(syst) {+-} 0.4(luminosity)pb which is consistent with the Standard Model.
Download or read book Measurement of the Ttbar Production Cross Section 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: A measurement of the t[bar t] production cross section in the lepton+jets channels with the D0 detector at [radical]s = 1.96 TeV using the lifetime-tagging techniques is presented. The t[bar t] cross section is estimated from the combination of the e+jets and [mu]+jets channels. The obtained result [sigma][sub tt][sup -] = 7.47 [sub -1.14][sup +1.22](stat)[sub -1.03][sup +1.65](syst) [+-] 0.49 (lumi) pb is consistent with the Standard Model expectation.
Download or read book Measurements of the T tbar Production Cross Section in Lepton jets Final States in Pp Collisions at 8 TeV and Ratio of 8 to 7 TeV Cross Sections written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the top quark pair production (t-tbar) cross section in proton-proton collisions at the centre-of-mass energy of 8 TeV is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6 inverse-femtobarns. This analysis is performed in the t-tbar decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured t-tbar cross section is 228.5 +/- 3.8 (stat) +/- 13.7 (syst) +/- 6.0 (lumi) pb. This measurement is compared with an analysis of 7 TeV data, corresponding to an integrated luminosity of 5.0 inverse-femtobarns, to determine the ratio of 8 TeV to 7 TeV cross sections, which is found to be 1.43 +/- 0.04 (stat) +/- 0.07 (syst) +/- 0.05 (lumi). The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.
Download or read book Measurement of the T bar T Production Cross Section at the Tevatron written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on the measurement of the t[anti t] production cross section obtained by CDF and D0 experiments with p[anti p] collisions at[radical]s=1. 8 TeV. The analyses presented here refer to[integral] Ldt[approx]11O pb[sup -1] collected at the Fermilab Tevatron collider during the run 1992-96. About 85% of the possible t[anti t] decays have been studied in different channels classified according to the number of high P[sub T] leptons found in the final state. The production cross section has been measured in each individual channel and then combined into a single value for each experiment, which is[sigma][sub tt]= 7.5[sup 1.9][sub 1.6] pb for CDF and[sigma][sub tt]= 5.77[+-] 1.76 pb for D0.
Download or read book Top Physics Measurement of the Cross Section for Ttbar Production in Ppbar Collisions Using the Kinematics of Lepton Jets Events written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Top Cross Section Measurement at CDF written by and published by . This book was released on 2010 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes the latest measurements of the t{bar t} pair production cross section performed by the CDF Collaboration analyzing p{bar p} collisions at a center-of-mass energy of 1.96 TeV from Fermilab Tevatron, as presented at the XVIII International Workshop on Deep-Inelastic Scattering and Related Subjects. In order to test Standard Model predictions, several analysis methods are explored and all the top decay channels are considered, to better constrain the properties of the top quark and to search for possible sources of new physics affecting the pair production mechanism. Experimental results using an integrated luminosity up to 5.1 fb−1 are presented.
Download or read book Measurement of the t bar t Production Cross Section in Pp Collisions at sqrt s written by and published by . This book was released on 2014 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Measurement of the Ttbar Production Cross Section in the All jets Final State in Pp Collisions at sqrt s written by and published by . This book was released on 2015 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cross section for tt production in the all-jets final state is measured in pp collisions at a centre-of-mass energy of 8 TeV at the LHC with the CMS detector, in data corresponding to an integrated luminosity of 18.4 fb-1. The inclusive cross section is found to be 275.6 ±6.1 (stat) ± 37.8 (syst) ± 7.2 (lumi) pb. The normalized differential cross sections are measured as a function of the top quark transverse momenta, pT, and compared to predictions from quantum chromodynamics. The results are reported at detector, parton, and particle levels. In all cases, the measured top quark pT spectra are significantly softer than theoretical predictions.
