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Recent Results In The Top Quark Sector From The D0 Experiment
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Book Synopsis Recent Results in the Top Quark Sector from the D0 Experiment by :
Download or read book Recent Results in the Top Quark Sector from the D0 Experiment written by and published by . This book was released on 2015 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: In these proceedings, I review recent measurements in the top quark sector in pp-bar collisions at a centre-of-mass energy of √s = 1.96 TeV in Run II of the Fermilab Tevatron Collider using the D0 detector. I will present the differential measurement of the tt-bar production cross section and the Tevatron combination of inclusive tt-bar cross section measurements; the first evidence of the production of single top quarks in the s-channel by D0 and the observation in combination with CDF. Furthermore, I will review the measurements of the forward-backward asymmetry in tt-bar events, and conclude with the world's most precise single measurement of the top quark mass, which is a fundamental parameter of the standard model, and present the Tevatron combination, which is the world's most precise determination of the top quark mass, with a relative precision of 0.37%.
Book Synopsis Studies of Top Quark Production at by :
Download or read book Studies of Top Quark Production at written by and published by . This book was released on 2011 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: I present recent results on top quark production in pp collisions at a center of mass energy of 1.96 TeV. The studies were performed by the D0 collaboration using approximately 5 fb−1 of data taken during Run II at the Fermilab Tevatron accelerator. The top quark is the heaviest known elementary particle and completes the quark sector of the three-generation structure of the standard model (SM). It differs from the other quarks not only by its much larger mass, but also by its lifetime which is too short to build hadronic bound states. The SM predicts that top quarks are created via two independent production mechanisms at hadron colliders. The primary mode, in which a t{bar t} pair is produced from a gtt vertex via the strong interaction, was used by the D0 and CDF collaborations to establish the existence of the top quark in 1995. The second production mode of top quarks at hadron colliders is the electroweak production of a single top quark from a Wtb vertex. The predicted cross section for single top quark production is about half that of t{bar t} pairs but the signal-to-background ratio is much worse; observation of single top quark production has therefore until recently been impeded by its low rate and difficult background environment compared to the top pair production. In the following sections I will present results for the measurement of the t{bar t} pair and the single top quark production cross section using respectively 5.3 fb−1 and 5.4 fb−1 of data taken by the D0 experiment.
Book Synopsis Recent D-Zero Results on the Top Quark by :
Download or read book Recent D-Zero Results on the Top Quark written by and published by . This book was released on 1997 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent results on top quark physics with the D0 experiment in {anti p}p collisions at √s = 1.8 TeV for an integrated luminosity of 125 pb−1 are reported. The direct measurement of the top quark mass uses single lepton events, giving the result m{sub top} = 173.3 ± 5.6(stat) ± 6.2(syst) GeV=c2. The measurement of the t{anti t} production cross section includes analyses from 8 top decay channels: dilepton (t{anti t} → e[mu], ee, and [mu][mu]), electron and neutrino (t{anti t} → e[nu]), and single leptons (t{anti t} → e + jets and t{anti t} → [mu] + jets) with and without b tagging. We measure the t{anti t} production cross section to be 5.5 ± 1.8 pb at m{sub top} = 173.3 GeV/c2.
Book Synopsis Recent Results on Top-Quark Physics at by :
Download or read book Recent Results on Top-Quark Physics at written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the most recent measurements on top-quark physics obtained with Tevatron $p\bar{p}$ collisions recorded by the D0 experiment at $\sqrt{s}= 1.96$ TeV. The full Run II data set of 9.7 fb$^{-1}$ is analyzed. Both lepton+jets and dilepton channels of top-quark pair production are used to measure the differential and inclusive cross sections, the forward-backward asymmetries, the top-quark mass, the spin correlations, and the top-quark polarization.
Book Synopsis Discovery of Single Top Quark Production by : Dag Gillberg
Download or read book Discovery of Single Top Quark Production written by Dag Gillberg and published by Springer Science & Business Media. This book was released on 2011-01-22 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is by far the heaviest known fundamental particle with a mass nearing that of a gold atom. Because of this strikingly high mass, the top quark has several unique properties and might play an important role in electroweak symmetry breaking—the mechanism that gives all elementary particles mass. Creating top quarks requires access to very high energy collisions, and at present only the Tevatron collider at Fermilab is capable of reaching these energies. Until now, top quarks have only been observed produced in pairs via the strong interaction. At hadron colliders, it should also be possible to produce single top quarks via the electroweak interaction. Studies of single top quark production provide opportunities to measure the top quark spin, how top quarks mix with other quarks, and to look for new physics beyond the standard model. Because of these interesting properties, scientists have been looking for single top quarks for more than 15 years. This thesis presents the first discovery of single top quark production. It documents one of the flagship measurements of the D0 experiment, a collaboration of more than 600 physicists from around the world. It describes first observation of a physical process known as “single top quark production”, which had been sought for more than 10 years before its eventual discovery in 2009. Further, his thesis describes, in detail, the innovative approach Dr. Gillberg took to this analysis. Through the use of Boosted Decision Trees, a machine-learning technique, he observed the tiny single top signal within an otherwise overwhelming background. This Doctoral Thesis has been accepted by Simon Fraser University, Burnaby, BC, Canada.
Download or read book D0 Findings on the Top Quark written by and published by . This book was released on 1998 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent results on top quark physics with the D0 experiment in pp collisions at (square root)s = 1.8 TeV are reported. The direct measurement of the top quark mass uses single lepton and dilepton events, giving the result m{sub top} = 172.1 " 7.1 GeV/c2 . The measurement of the t{anti t} production cross section includes analyses from 9 top decay channels: dilepton, electron and neutrino, single leptons with and without b tagging, and all-jets (t{anti t} --> b jets). The authors measured the t{anti t} production cross section to be 5.9 " 1.7 pb at m{sub top} = 172.1 GeV/c2. Preliminary results on a search for charged Higgs production in top events are presented.
Book Synopsis Top Quark Results from by : H. B. Greenlee
Download or read book Top Quark Results from written by H. B. Greenlee and published by . This book was released on 2005 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this talk I will present recent preliminary results from the D0 experiment from Tevatron Run II (p{bar p} collisions at {radical}s = 1.96 TeV). The results presented in this talk include top quark pair production cross section, top quark mass, and upper limits on single top quark production.
Book Synopsis Measurements and Searches with Top Quarks by :
Download or read book Measurements and Searches with Top Quarks written by and published by . This book was released on 2008 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1995 the last missing member of the known families of quarks, the top quark, was discovered by the CDF and D0 experiments at the Tevatron, a proton-antiproton collider at Fermilab near Chicago. Until today, the Tevatron is the only place where top quarks can be produced. The determination of top quark production and properties is crucial to understand the Standard Model of particle physics and beyond. The most striking property of the top quark is its mass--of the order of the mass of a gold atom and close to the electroweak scale--making the top quark not only interesting in itself but also as a window to new physics. Due to the high mass, much higher than of any other known fermion, it is expected that the top quark plays an important role in electroweak symmetry breaking, which is the most prominent candidate to explain the mass of particles. In the Standard Model, electroweak symmetry breaking is induced by one Higgs field, producing one additional physical particle, the Higgs boson. Although various searches have been performed, for example at the Large Electron Positron Collider (LEP), no evidence for the Higgs boson could yet be found in any experiment. At the Tevatron, multiple searches for the last missing particle of the Standard Model are ongoing with ever higher statistics and improved analysis techniques. The exclusion or verification of the Higgs boson can only be achieved by combining many techniques and many final states and production mechanisms. As part of this thesis, the search for Higgs bosons produced in association with a top quark pair (t{bar t}H) has been performed. This channel is especially interesting for the understanding of the coupling between Higgs and the top quark. Even though the Standard Model Higgs boson is an attractive candidate, there is no reason to believe that the electroweak symmetry breaking is induced by only one Higgs field. In many models more than one Higgs boson are expected to exist, opening even more channels to search for charged or neutral Higgs bosons. Depending on its mass, the charged Higgs boson is expected to decay either into top quarks or be the decay product of a top quark. For masses below the top quark mass, the top decay into a charged Higgs boson and a b quark can occur at a certain rate, additionally to the decays into W bosons and a b quark. The different decays of W and charged Higgs bosons can lead to deviations of the observed final number of events in certain final states with respect to the Standard Model expectation. A global search for charged Higgs bosons in top quark pair events is presented in this thesis, resulting in the most stringent limits to-date. Besides the decay of top quarks into charged Higgs or W bosons, new physics can also show up in the quark part of the decay. While in the Standard Model the top quark decays with a rate of about 100% into a W boson and a b quark, there are models where the top quark can decay into a W boson and a non-b quark. The ratio of branching fractions in which the top quark decays into a b quark over the branching fractions in which the top quark decays into all quarks is measured as part of this thesis, yielding the most precise measurement today. Furthermore, the Standard Model top quark pair production cross section is essential to be known precisely since the top quark pair production is the main background for t{bar t}H production and many other Higgs and beyond the Standard Model searches. However, not only the search or the test of the Standard Model itself make the precise measurement of the top quark pair production cross section interesting. As the cross section is calculated with high accuracy in perturbative QCD, a comparison of the measurement to the theory expectation yields the possibility to extract the top quark mass from the cross section measurement. Although many dedicated techniques exist to measure the top quark mass, the extraction from the cross section represents an important complementary measurement. The latter is briefly discussed in this thesis and compared to direct top mass measurements. The goal of this thesis is the improved understanding of the top quark sector and its use as a window to new physics. Techniques are extended and developed to measure the top quark pair production cross section simultaneously with the ratio of branching fractions, the t{bar t}H cross section or the rate with which top quarks decay into charged Higgs bosons. Some of the results are then taken to extract more information. The cross section measurement is used to extract the top quark mass, and the ratio of the top quark pair production cross sections in different final states, yielding a limit on non-Standard Model top quark decays.
Download or read book Heavy Quark Results at written by and published by . This book was released on 1997 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent results in heavy quark physics from the D0 experiment at the Fermilab Tevatron Collider are reported. Topics included are top quark production and mass determination, bottom production and correlations, and charmonium production. 20 refs., 10 figs., 2 tabs.
Book Synopsis Top Quark Physics at the D0 Experiment by :
Download or read book Top Quark Physics at the D0 Experiment written by and published by . This book was released on 1996 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper I present the latest results on top quark physics from the D0 collaboration since the discovery of the top quark in March 1995. I summarize the discovery results, discuss progress since the discovery, and show how we can measure the top quark mass using three separate techniques. The measurements were made at the Fermilab Tevatron, a p{bar p} collider with (square root)s = TeV, using (approximately)50 pb−1 data collected from 1992 to early 1995.
Download or read book The Top Quark and More written by and published by . This book was released on 1996 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper we describe some highlights of recent physics results from the D0 experiment at the Tevatron {bar p}p collider. One aspect of recent QCD experimentation has been the emphasis on studies of events with rapidity gaps; the characteristics of such events in the D0 data are described. The non-abelian nature of the electroweak interaction is a well defined property of the standard model. The very high energies available at the Tevatron have opened a new window which permits the testing of this aspect of the standard model. The highlight among recent results was the observation of the top quark and this result is discussed. At the highest energy available, D0 is conducting numerous searches for phenomena which might indicate the structure of the world beyond the electroweak scale. We discuss searches for the particles of supersymmetry. The luminosity of the collider will increase dramatically over the next five years. This will open new fields of investigation for an upgraded D0 detector.
Book Synopsis Studies of the Top Quark with the D0 Detector by :
Download or read book Studies of the Top Quark with the D0 Detector written by and published by . This book was released on 1996 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The observation of the top quark by the D0 experiment, at Fermilab's Tevatron proton-antiproton collider, is briefly reviewed. The analysis of the top quark mass in the lepton plus jets decay channels, resulting in m{sub t} (almost equal to) 200 GeV/c2 is reviewed; and a preliminary mass analysis from the dilepton decay channels resulting in m{sub t} = 145 " 25 (statistical) " 20 (systematic) GeV/c2 is presented. These mass measurements are compared with Standard Model limits from CERN's LEP experiments and the published CDF measurement. Preliminary observation of top quark-W boson correlation is shown.
Download or read book Top Quark Mass written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A summary of the most up-to-date top quark mass measurements at CDF is presented. These analyses use top-antitop candidate events detected in the CDF experiment at the Tevatron collider with an integrated luminosity of up to (almost equal to)3/fb. The combination of all those measurements together with the corresponding top mass measurements from the concurrently running D0 experiment at the Tevatron yields a world average of M{sub t} = [173.1 ± 0.6(stat.) ± 1.1(syst.)] GeV/c2.
Book Synopsis Combination of CDF and D0 Results on the Mass of the Top Quark Using Up to 9.7 Fb$^{-1}$ at the Tevatron by :
Download or read book Combination of CDF and D0 Results on the Mass of the Top Quark Using Up to 9.7 Fb$^{-1}$ at the Tevatron written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Top Quark Production at the Tevatron by :
Download or read book Top Quark Production at the Tevatron written by and published by . This book was released on 2011 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the most recently discovered of the standard model quarks, and because of its very large mass, studies of the top quark and its interactions are important both as tests of the standard model and searches for new phenomena. In this document, recent results of analyses of top quark production, via both the electroweak and strong interactions, from the CDF and D0 experiments are presented. The results included here utilize a dataset corresponding to up to 6 fb−1 of integrated luminosity, slightly more than half of the dataset recorded by each experiment before the Tevatron was shutdown in September 2011.
Book Synopsis Measurements and Searches with Top Quarks by : Yvonne Peters
Download or read book Measurements and Searches with Top Quarks written by Yvonne Peters and published by . This book was released on 2008 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Top-mass Measurements from written by and published by . This book was released on 2009 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present three recent analyses (Abstracts 169, 170 and 174) of the mass of the top quark (M{sub t}) using top-antitop candidate events collected by the D0 experiment at the Fermilab Tevatron Collider: (i) a 3.6 events/fb sample of data in the lepton+jets channel analyzed to extract a precision value of M{sub t} using the 'Matrix-Element' (ME) method, wherein each event probability is calculated from the differential production cross section as a function of M{sub t} and the overall jet energy scale, with the latter constrained by the two jets from W decay into q(prime){bar q}, (ii) a first measurement of the mass difference between top and antitop quarks as a check of CPT invariance in the quark sector, also based on the ME method in lepton+jets channels, and corresponding to a 1 event/fb data sample, and (iii) measurements of M{sub t} in dilepton final states (updated to 3.6 events/fb), based on 'matrix' weighting, 'neutrino' weighting and the ME method, which rely, respectively, on the likelihood of observing the events in data for a range of assumed M{sub t} values, distributions generated from event weights that compare calculated and reconstructed missing transverse energies, and event probabilities based on the leading-order differential cross section as a function of assumed M{sub t}. In addition, we provide a combination of recent top-mass measurements from D0.
