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Search For The Top Quark In Dilepton Decay Modes At
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Book Synopsis Search for the Top Quark in Dilepton Decay Modes at by :
Download or read book Search for the Top Quark in Dilepton Decay Modes at written by and published by . This book was released on 1995 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present preliminary results on the search for the top quark in p{bar p} collisions at √s = 1.8 TeV by the D0 collaboration at the Fermilab Tevatron. The results are based on an integrated luminosity of 13.5 pb−1 of data collected by the D0 detector during the 1992-3 Tevatron collider run. They have searched for Standard Model t{bar t} decays into the dilepton decay modes ee + X, e[mu] + X and [mu][mu] + X. No significant signal is observed for top quark production in these channels. They find one candidate event in the e[mu] + X channel and no events in the other two channels with an estimated non-top background of 0.76 ± 0.16 events.
Book Synopsis A Search for Top Quark Pair Production in the Dilepton Decay Mode by : James C. Romano
Download or read book A Search for Top Quark Pair Production in the Dilepton Decay Mode written by James C. Romano and published by . This book was released on 1995 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for the Top Quark in the Single Lepton + Jets Channel at by :
Download or read book Search for the Top Quark in the Single Lepton + Jets Channel at written by and published by . This book was released on 1993 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have searched for standard model top quark pair production at (square root)s = 1.8 TeV. We present preliminary results of searches in the single lepton decay modes (i.e. where one top quark decays semileptonically to an electron or a muon and the other top quark decayed hadronically). We do not find evidence for top quark production in these decay channels. By combining this negative result with our negative result from the dilepton decay channels, we obtain a 95% confidence level upper limit on the top quark production cross section for top masses between 80 and 140 GeV/c2. By comparing this cross section upper limit curve with a theoretical production cross section we obtain a lower limit on the top quark mass of 124 GeV/c2.
Book Synopsis The Evidence for the Top Quark by : Kent W. Staley
Download or read book The Evidence for the Top Quark written by Kent W. Staley and published by Cambridge University Press. This book was released on 2004-04-05 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Evidence for the Top Quark offers both a historical and philosophical perspective on an important recent discovery in particle physics: the first evidence for the elementary particle known as the top quark. Drawing on published reports, oral histories, and internal documents from the large collaboration that performed the experiment, Kent Staley explores in detail the controversies and politics that surrounded this major scientific result.At the same time the book seeks to defend an objective theory of scientific evidence based on error probabilities.
Book Synopsis On Measuring the Top Quark Mass Using the Dilepton Decay Modes by :
Download or read book On Measuring the Top Quark Mass Using the Dilepton Decay Modes written by and published by . This book was released on 1996 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: We demonstrate a new likelihood method for extracting the top quark mass from events of the type {ital t}{ital {anti t}} --> {ital b}W({ital lepton+{nu}}){ital {anti b}}W−({ital lepton+{nu}}). This method estimates the top quark mass correctly from an ensemble of dilepton events. The method proposed by Dalitz and Goldstein is shown to result in a systematic underestimation of the top quark mass. Effects due to the spin correlations between the top and anti-top quarks are shown to be unimportant in estimating the mass of the top quark.
Book Synopsis Search for Direct Pair Production of Scalar Top Quarks in the Single- and Dilepton Channels in Proton-proton Collisions at $\sqrt{s}$ by :
Download or read book Search for Direct Pair Production of Scalar Top Quarks in the Single- and Dilepton Channels in Proton-proton Collisions at $\sqrt{s}$ written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are reported from a search for the top squark $ \tilde{t}_1 $, the lighter of the two supersymmetric partners of the top quark. The data sample corresponds to 19.7 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} =$ 8 TeV collected with the CMS detector at the LHC. The search targets $ \tilde{t}_1 \to \mathrm{b} \tilde{\chi}^{\pm}_1$ and $ \tilde{t}_1 \to \mathrm{t}^{(*)} \tilde{\chi}^0_1$ decay modes, where $\tilde{\chi}^{\pm}_1$ and $\tilde{\chi}^0_1$ are the lightest chargino and neutralino, respectively. The reconstructed final state consists of jets, b jets, missing transverse energy, and either one or two leptons. Leading backgrounds are determined from data. No significant excess in data is observed above the expectation from standard model processes. The results exclude a region of the two-dimensional plane of possible $ \tilde{t}_1 $ and $\tilde{\chi}^0_1 $ masses. The highest excluded $ \tilde{t}_1 $ and $ \tilde{\chi}^0_1$ masses are about 700 GeV and 250 GeV, respectively.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Observation of Top Quarks in the Dilepton Decay Channel T{anti T} 2!e([mu][upsilon]{sub E({mu})} [tau][upsilon]{sub {tau}} B{anti B} Using Hadronic Tau Decays at CDF. by :
Download or read book Observation of Top Quarks in the Dilepton Decay Channel T{anti T} 2!e([mu][upsilon]{sub E({mu})} [tau][upsilon]{sub {tau}} B{anti B} Using Hadronic Tau Decays at CDF. written by and published by . This book was released on 1996 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for dilepton events from top decays with one electron or muon and a hadronically decaying [tau] lepton. The total acceptance x efficiency is (O.119 ± 0.014({ital stat}))% for {ital m{sub top}} = 175 GeV. In 110 pb−1 of data we expect 1.1 ± 0. 3({ital stat}) signal events and a total background of 1.96 ± 0.35({ital stat}) events while observing 4 candidate events (2 {ital e}[tau] and 2 [mu][tau]). Three events are {ital b}-tagged. If a tag is required, the probability for the estimated background (0.225 ± 0.011 events) to fluctuate to ≥ 3 events is 0.13% (3.0 [sigma]). A first measurement of the {ital t{anti t}} production cross section based on these events yields [sigma]{sub t{anti t}} = 15.6{sup +18. 6}{sub -13.2}({ital stat}) pb.
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.
Book Synopsis Search for a Vector-like Quark T' Decaying Into Top+Higgs in Single Production Mode in Full Hadronic Final State Using CMS Data Collected at 8 TeV by : José David Ruiz Alvarez
Download or read book Search for a Vector-like Quark T' Decaying Into Top+Higgs in Single Production Mode in Full Hadronic Final State Using CMS Data Collected at 8 TeV written by José David Ruiz Alvarez and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: During 2012, the Large Hadron Collider (LHC) has delivered proton-proton collisions at 8 TeV center of mass energy to the ATLAS and CMS experiments. These two experiments have been designed to discover the Higgs boson and to search for new particles predicted by several theoretical models, as supersymmetry. The Higgs boson has been discovered by ATLAS and CMS experiments on July, 4th of 2012, starting a new era of discoveries in particle physics domain. With the confirmation of the existence of the Higgs boson, searches for new physics involving this boson are of major interest. In particular, data can be used to look for new massive particles that decay into the Higgs boson accompanied with other particles of the standard model. One expected signature is a Higgs boson produced with a top quark, the two heaviest particles in the standard model. The standard model predicts a cross section of top-Higgs production, then any enhancement of their associated production will be a clear signature of physics beyond the standard model. In addition, the existence of physics beyond the standard model can also be reflected by resonances that decay into a top-quark and a Higgs boson. In the first part of my work I describe the theoretical and experimental foundations of the standard model, as well as the experimental device. In the same theoretical chapter, I also discuss the formulation of an extension of the standard model. In addition, I describe a feasibility study of a search of one of the particles predicted by such model. The second part contains the realization of the search for a top partner, T_, within the CMS experiment. This top partner is a new particle very similar to the standard model top quark, but much heavier, that can decay into a top quark and a Higgs boson. The analysis looks for this particle in the full hadronic final state, where the Higgs boson decays into two b-quarks and the top quark decays into three standard model quarks, a b and two light quarks. In this channel, I reconstruct its mass from the identification of all its decay products. As a result of the analysis, I show the limits on the T_ production cross section from the number of observed events in the specific signature.
Book Synopsis Physics at the Large Hadron Collider by : Amitava Datta
Download or read book Physics at the Large Hadron Collider written by Amitava Datta and published by Springer Science & Business Media. This book was released on 2010-05-30 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an epoch when particle physics is awaiting a major step forward, the Large Hydron Collider (LHC) at CERN, Geneva will soon be operational. It will collide a beam of high energy protons with another similar beam circulation in the same 27 km tunnel but in the opposite direction, resulting in the production of many elementary particles some never created in the laboratory before. It is widely expected that the LHC will discover the Higgs boson, the particle which supposedly lends masses to all other fundamental particles. In addition, the question as to whether there is some new law of physics at such high energy is likely to be answered through this experiment. The present volume contains a collection of articles written by international experts, both theoreticians and experimentalists, from India and abroad, which aims to acquaint a non-specialist with some basic issues related to the LHC. At the same time, it is expected to be a useful, rudimentary companion of introductory exposition and technical expertise alike, and it is hoped to become unique in its kind. The fact that there is substantial Indian involvement in the entire LHC endeavour, at all levels including fabrication, physics analysis procedures as well as theoretical studies, is also amply brought out in the collection.
Download or read book Dark Decay of Top Quark written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We suggest top quark decays as a venue to search for light dark force carriers. Top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6 [sigma] deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t → b W + Z's. This is the same as the dominant top quark decay (t → b W) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. We discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.
Download or read book The Particle Century written by G Fraser and published by CRC Press. This book was released on 1998-01-01 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the first attempts to split the atom to the discovery of the top quark, the 20th century has witnessed a revolution in basic physics. Probing successively smaller constituents of matter has also revealed the conditions present at the time of the Big Bang. In a series of essays by scientists who have been closely involved in this exciting research, The Particle Century describes the unprecedented advances in our understanding of the universe. The book covers major historical developments as well as current advances, including early accelerator physics, the rise of the Standard Model, new comprehension of the big bang theory, and the cutting edge of today's investigations. These essays add novel insight into the continuing efforts to unravel the deepest secrets of nature.
Book Synopsis Quarks And Colliders - Proceedings Of The Tenth Lake Louise Winter Institute by : Alan Astbury
Download or read book Quarks And Colliders - Proceedings Of The Tenth Lake Louise Winter Institute written by Alan Astbury and published by World Scientific. This book was released on 1996-08-22 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book originated in a series of lectures given at Liverpool in 2013 to a group that included postgraduate and undergraduate students and staff of the Physics Department. They followed from two very successful lectures given to the undergraduate Physical Society. It seemed that there was a very large interest among the students in investigating the foundations of physics in a way that was never done in physics courses, and was not available in books or other outlets. However, the idea was to create a framework in which students (and interested staff) could develop their own thinking relative to the ideas in the lectures. So it was important to create both conceptual and mathematical structures on the issues that are important at this level. The book has the right sort of technical content to allow for this development, but doesn't lose itself in excessive details. The ideal use for this book would be on postgraduate courses where students would be encouraged to think about the foundations in a way that is well beyond the superficial. However, a course on aspects of this material would also be valuable at the undergraduate level, where students could be stimulated into believing that creative thinking could solve the problems that emerge when we confront foundational problems.
Book Synopsis Observation of Top Quarks in the Dilepton Decay Channel T[anti T][yields] E([mu][upsilon][sub E([mu][tau][upsilon][sub[tau] B[anti B] Using Hadronic Tau Decays at CDF. by :
Download or read book Observation of Top Quarks in the Dilepton Decay Channel T[anti T][yields] E([mu][upsilon][sub E([mu][tau][upsilon][sub[tau] B[anti B] Using Hadronic Tau Decays at CDF. written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for dilepton events from top decays with one electron or muon and a hadronically decaying[tau] lepton. The total acceptance x efficiency is (O.119[+-] 0.014([ital stat]))% for[ital m[sub top]]= 175 GeV. In 110 pb[sup -1] of data we expect 1.1[+-] 0. 3([ital stat]) signal events and a total background of 1.96[+-] 0.35([ital stat]) events while observing 4 candidate events (2[ital e][tau] and 2[mu][tau]). Three events are[ital b]-tagged. If a tag is required, the probability for the estimated background (0.225[+-] 0.011 events) to fluctuate to[>=] 3 events is 0.13% (3.0[sigma]). A first measurement of the[ital t[anti t]] production cross section based on these events yields[sigma][sub t[anti t]]= 15.6[sup+18. 6][sub -13.2]([ital stat]) pb.
Book Synopsis Top Quark Search in the Dilepton Channel in 1.8-TeV Proton - Anti-proton Collisions by :
Download or read book Top Quark Search in the Dilepton Channel in 1.8-TeV Proton - Anti-proton Collisions written by and published by . This book was released on 1994 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the top quark (t) in p$\bar{p}$ collisions at √s = 1.8 TeV is described. We consider the t$\bar{t }$ pairs, followed by semileptonoic decays via real w bosons: t$\bar{t }$ → W+b W-$\bar{b}$ l1l2X, where l1 and l2 are electrons and muons.
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.
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