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Evidence For Single Top Quark Production At
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Book Synopsis Evidence for Single Top Quark Production at by :
Download or read book Evidence for Single Top Quark Production at written by and published by . This book was released on 2007 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of the first analysis to show evidence for production of single top quarks are presented. Using 0.9 fb-1 of data collected with the D0 detector at the Fermilab Tevatron, the analysis is performed in the electron jets and muon jets decay modes, taking special care in modeling the large backgrounds, applying a new powerful b-quark tagging algorithm and using three multivariate techniques to extract the small signal in the data. The combined measured production cross section is 4.8 +- 1.3 pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.027%, corresponding to a 3.5 standard deviation significance.
Book Synopsis Evidence for S-channel Single Top Quark Production in $p\bar{p}$ Collisions at $\sqrt{s}$ by :
Download or read book Evidence for S-channel Single Top Quark Production in $p\bar{p}$ Collisions at $\sqrt{s}$ written by and published by . This book was released on 2013 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Book Synopsis Evidence for Production of Single Top Quarks by :
Download or read book Evidence for Production of Single Top Quarks written by and published by . This book was released on 2008 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p{bar p} collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top quark partner that is always produced from strong coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top quark production has been searched for in ever larger datasets. In this analysis, we select events from a 0.9 fb−1 dataset that have an electron or muon and missing transverse energy from the decay of a W boson from the top quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W+jets and t{bar t} events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top quark production of [sigma](p{bar p} → tb + X, tqb + X) = 4.7 ± 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find.
Download or read book Single Top Quark Production at written by and published by . This book was released on 2008 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present first evidence for the production of single top quarks at the Fermilab Tevatron p{bar p} collider. Using a 0.9 fb−1 dataset, we apply a multivariate analysis to separate signal from background and measure cross section for single top quark production. We use the cross section measurement to directly determine the CKM matrix element that describes the Wtb coupling. We also present results of W0 and charged Higgs searches with the same final states as standard model single top quark production.
Book Synopsis Evidence for Single Top Quark Production Using Bayesian Neural Networks by : Daekwang Kau
Download or read book Evidence for Single Top Quark Production Using Bayesian Neural Networks written by Daekwang Kau and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: We present results of a search for single top quark production in pp collisions using adataset of approximately 1 fb-1 collected with the DØ detector. This analysis considers the muon+jets and electron+jets final states and makes use of Bayesian neural networks to separate the expected signals from backgrounds. The observed excess is associated with a p-value of 0.081%, assuming the background-only hypothesis, which corresponds to an excess over background of 3.2 standard deviations for a Gaussian density. The p-value computed using the SM signal cross section of 2.9 pb is 1.6%, corresponding to an expected significance of 2.2 standard deviations. Assuming the observed excess is due to single top production, we measure a single top quark production cross section of (p p! tb+X, tqb+X) = 4.4"1.5 pb.
Book Synopsis Evidence for Single Top Quark Production Using Bayesian Neural Networks by :
Download or read book Evidence for Single Top Quark Production Using Bayesian Neural Networks written by and published by . This book was released on 2007 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present results of a search for single top quark production in p{bar p} collisions using a dataset of approximately 1 fb−1 collected with the D0 detector. This analysis considers the muon+jets and electron+jets final states and makes use of Bayesian neural networks to separate the expected signals from backgrounds. The observed excess is associated with a p-value of 0.081%, assuming the background-only hypothesis, which corresponds to an excess over background of 3.2 standard deviations for a Gaussian density. The p-value computed using the SM signal cross section of 2.9 pb is 1.6%, corresponding to an expected significance of 2.2 standard deviations. Assuming the observed excess is due to single top production, we measure a single top quark production cross section of [sigma](p{bar p} → tb + X, tqb + X) = 4.4 ± 1.5 pb.
Book Synopsis Observation of Single Top Quark Production by :
Download or read book Observation of Single Top Quark Production written by and published by . This book was released on 2009 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The author reports on the observation of electroweak production of single top quarks in p{bar p} collisions at (square root)s = 1.96 Tev using 2.3 fb−1 of data collected with the D0 detector at the fermilab Tevatron Collider. Using events containing an isolated electron or muon, missing transverse energy, two, three or four jets, with one or two of them identified as originating from the fragmentation of a b quark, the measured cross section for the process p{bar p} --> tb + X, tqb + X is 3.94 ± 0.88 pb (for a top quark mass of 170 GeV). the probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10−7, corresponding to a 5.0 standard deviation significance. Using the same dataset, the measured cross sections for the t- and the s-channel processes when determined simultaneously with no assumption on their relative production rate are 3.14{sub -0.80}{sup +0.94} pb and 1.05 ± 0.81 pb respectively, consistent with standard model expectations. The measured t-channel cross section has a significance of 4.8 standard deviations, representing the first evidence for the production of an individual single top process to be detected.
Book Synopsis Evidence for Electroweak Top Quark Production in Proton-antiproton Collisions at S**1/2 by :
Download or read book Evidence for Electroweak Top Quark Production in Proton-antiproton Collisions at S**1/2 written by and published by . This book was released on 2007 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the first evidence for electroweak single top quark production using nearly 1 fb−1 of Tevatron Run II data at √s = 1.96 TeV. We select single-top-like data events in the lepton+jets decay channel and separate them from backgrounds using the matrix element analysis method. This technique uses leading order matrix elements to compute an event probability for both signal and background hypotheses. Using the expected signal acceptance, background, and observed data we measure the single top quark cross section: [sigma](p{bar p} → tb + tqb + X) = 4.6{sub -1.5}+1.8 pb. The probability for the background to have fluctuated up to give at least the cross section measured in this analysis is 0.21%, which corresponds to a Gaussian equivalent significance of 2.9[sigma].
Book Synopsis Measurement of the T-channel Single Top Quark Production Cross Section by :
Download or read book Measurement of the T-channel Single Top Quark Production Cross Section written by and published by . This book was released on 2009 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The D0 collaboration reports direct evidence for electroweak production of single top quarks through the t-channel exchange of a virtual W boson. This is the first analysis to isolate an individual single top quark production channel. We select events containing an isolated electron or muon, missing transverse energy, and two, three or four jets from 2.3 fb−1 of p{bar p} collisions at the Fermilab Tevatron Collider. One or two of the jets are identified as containing a b hadron. We combine three multivariate techniques optimized for the t-channel process to measure the t- and s-channel cross sections simultaneously. We measure cross sections of 3.14{sub -0.80}{sup +0.94} pb for the t-channel and 1.05 ± 0.81 pb for the s-channel. The measured t-channel result is found to have a significance of 4.8 standard deviations and is consistent with the standard model prediction.
Book Synopsis Search for Single Top Quark Production in P Anti-p Collisions at S**1/2 by :
Download or read book Search for Single Top Quark Production in P Anti-p Collisions at S**1/2 written by and published by . This book was released on 2005 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for electroweak production of single top quarks in the s-channel and t-channel using neural networks for signal-background separation. We have analyzed 230 pb−1 of data collected with the D0 detector at the Fermilab Tevatron Collider at a center-of-mass energy of 1.96 TeV and find no evidence for a single top quark signal. The resulting 95% confidence level upper limits on the single top quark production cross sections are 6.4 pb in the s-channel and 5.0 pb in the t-channel.
Book Synopsis Evidence for Single Top-quark Production in the S-channel in Proton{u2013}proton Collisions at {u221A}s by :
Download or read book Evidence for Single Top-quark Production in the S-channel in Proton{u2013}proton Collisions at {u221A}s written by and published by . This book was released on 2016 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Letter presents evidence for single top-quark production in the s-channel using proton–proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS detector at the CERN Large Hadron Collider. The analysis is performed on events containing one isolated electron or muon, large missing transverse momentum and exactly two b-tagged jets in the final state. The analysed data set corresponds to an integrated luminosity of 20.3 fb-1. The signal is extracted using a maximum-likelihood fit of a discriminant which is based on the matrix element method and optimized in order to separate single-top-quark s-channel events from the main background contributions, which are top-quark pair production and W boson production in association with heavy-flavour jets. The measurement leads to an observed signal significance of 3.2 standard deviations and a measured cross-section of ?s = 4.8 ± 0.8(stat.)-1.3+1.6(syst.) pb, which is consistent with the Standard Model expectation. As a result, the expected significance for the analysis is 3.9 standard deviations.
Book Synopsis Single Top Quark Production at the Tevatron by :
Download or read book Single Top Quark Production at the Tevatron written by and published by . This book was released on 2008 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Tevatron experiments D0 and CDF have found evidence for single top quark production, based on datasets between 0.9 fb−1 and 2.2 fb−1. Several different multivariate techniques are used to extract the single top quark signal out of the large backgrounds. The cross section measurements are also used to provide the first direct measurement of the CKM matrix element.
Book Synopsis Measurement of the Single Top Quark Production Cross Section at $\sqrt {s} by :
Download or read book Measurement of the Single Top Quark Production Cross Section at $\sqrt {s} written by and published by . This book was released on 2011 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Within the standard model top quarks are predicted to be most often produced in pairs via the strong interaction. However they can also be produced singly through the weak interation. This is a rarer process with many experimental challenges. It is interesting because it provides a new window to search for evidence of physics beyond the standard model picture, such as a fourth generation of quarks or to search for insight into the Higgs Mechanism. Single top production also provides a direct way to calculate the CKM matrix element Vtb. This thesis presents new measurements for single top quark production in the s+t, s and t channels using 5.4 fb-1 of data collected at the DØ detector at Fermilab in Batavia, IL. The analysis was performed using Boosted decision trees to separate signal from background and Bayesian statistcs to calculate all the cross sections.
Book Synopsis Single Top Quarks at the Tevatron by :
Download or read book Single Top Quarks at the Tevatron written by and published by . This book was released on 2008 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: After many years searching for electroweak production of top quarks, the Tevatron collider experiments have now moved from obtaining first evidence for single top quark production to an impressive array of measurements that test the standard model in several directions. This paper describes measurements of the single top quark cross sections, limits set on the CKM matrix element.
Book Synopsis Search for Anomalous Single Top Quark Production in Association with a Photon in Pp Collisions at {u221A}(s) by :
Download or read book Search for Anomalous Single Top Quark Production in Association with a Photon in Pp Collisions at {u221A}(s) written by and published by . This book was released on 2016 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: We found the results of a search for flavor changing neutral currents (FCNC) through single top quark production in association with a photon is presented. The study is based on proton-proton collisions at a center-of-mass energy of 8 TeV using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 fb-1. The search for t? events where t → Wb andW → ?n is conducted in final states with a muon, a photon, at least one hadronic jet with at most one being consistent with originating from a bottom quark, and missing transverse momentum. Furthermore, there was no evidence of single top quark production in association with a photon through a FCNC is observed. Upper limits at the 95% confidence level are set on the tug and tcg anomalous couplings and translated into upper limits on the branching fraction of the FCNC top quark decays: B(t → u?) 1.3 x 10sup-4/sup and B(t →c?) 1.7 x 10
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.
