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Measurement Of Single Top Quark Production In The Tau Jets Channnel Using Boosted Decision Trees At
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Book Synopsis Measurement of Single Top Quark Production in the Tau+jets Channel Using Boosted Decision Trees at D0 by : Zhiyi Liu
Download or read book Measurement of Single Top Quark Production in the Tau+jets Channel Using Boosted Decision Trees at D0 written by Zhiyi Liu and published by . This book was released on 2009 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the heaviest known matter particle and plays an important role in the Standard Model of particle physics. At hadron colliders, it is possible to produce single top quarks via the weak interaction. This allows a direct measurement of the CKM matrix element Vtb and serves as a window to new physics. The first direct measurement of single top quark production with a tau lepton in the final state (the tau+jets channel) is presented in this thesis. The measurement uses 4.8 fb1 of Tevatron Run II data in p\bar{p} collisions at \sqrt{s}=1.96 TeV acquired by the D0 experiment. After selecting a data sample and building a background model, the data and background model are in good agreement. A multivariate technique, boosted decision trees, is employed in discriminating the small single top quark signal from a large background. The expected sensitivity of the tau+jets channel in the Standard Model is 1.8 standard deviations. Using a Bayesian statistical approach, an upper limit on the cross section of single top quark production in the tau+jets channel is measured as 7.3 pb at 95% confidence level, and the cross section is measured as 3.4+2.0−1.8 pb. The result of the single top quark production in the tau+jets channel is also combined with those in the electron+jets and muon+jets channels. The expected sensitivity of the electron, muon and tau combined analysis is 4.7 standard deviations, to be compared to 4.5 standard deviations in electron and muon alone. The measured cross section in the three combined final states is sigma(p\bar{p}->tb+X,tqb+X) = 3.84+0.89−0.83 pb. A lower limit on Vth is also measured in the three combined final states to be alrger than 0.85 at 95% confidence level. These results are consistent with Standard Model expectations.
Book Synopsis Measurement of Single Top Quark Production in the Tau+jets Channnel Using Boosted Decision Trees at by :
Download or read book Measurement of Single Top Quark Production in the Tau+jets Channnel Using Boosted Decision Trees at written by and published by . This book was released on 2009 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the heaviest known matter particle and plays an important role in the Standard Model of particle physics. At hadron colliders, it is possible to produce single top quarks via the weak interaction. This allows a direct measurement of the CKM matrix element V{sub tb} and serves as a window to new physics. The first direct measurement of single top quark production with a tau lepton in the final state (the tau+jets channel) is presented in this thesis. The measurement uses 4.8 fb−1 of Tevatron Run II data in p{bar p} collisions at √s = 1.96 TeV acquired by the D0 experiment. After selecting a data sample and building a background model, the data and background model are in good agreement. A multivariate technique, boosted decision trees, is employed in discriminating the small single top quark signal from a large background. The expected sensitivity of the tau+jets channel in the Standard Model is 1.8 standard deviations. Using a Bayesian statistical approach, an upper limit on the cross section of single top quark production in the tau+jets channel is measured as 7.3 pb at 95% confidence level, and the cross section is measured as 3.4{sub -1.8}{sup +2.0} pb. The result of the single top quark production in the tau+jets channel is also combined with those in the electron+jets and muon+jets channels. The expected sensitivity of the electron, muon and tau combined analysis is 4.7 standard deviations, to be compared to 4.5 standard deviations in electron and muon alone. The measured cross section in the three combined final states is [sigma](p{bar p} → tb + X,tqb + X) = 3.84{sub -0.83}{sup +0.89} pb. A lower limit on.
Book Synopsis Measurement of $\boldsymbol{\ttb}$ Production in the Tau + Jets Channel Using $\boldsymbol{p\bar{p}}$ Collisions at $\boldsymbol{\sqrt{s} by :
Download or read book Measurement of $\boldsymbol{\ttb}$ Production in the Tau + Jets Channel Using $\boldsymbol{p\bar{p}}$ Collisions at $\boldsymbol{\sqrt{s} written by and published by . This book was released on 2010 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the t{bar t} production cross section multiplied by the branching ratio to tau lepton decaying semi-hadronically ([tau]{sub h}) plus jets, [sigma](p{bar p} → t{bar t} + X) · BR(t{bar t} → [tau]{sub h} + jets), at a center of mass energy √s = 1.96 TeV using 1 fb−1 of integrated luminosity collected with the D0 detector. Assuming a top quark mass of 170 GeV, we measure [sigma]{sub t{bar t}} · BR{sub [tau]{sub h}+j} = 0.60{sub -0.22}{sup +0.23}(stat){sub -0.14}{sup +0.15}(syst)±0.04 (lumi) pb. In addition, we extract the t{bar t} production cross section using the t{bar t} → {tau}{sub h} + jets topology, with the result [sigma]{sub t{bar t}} = 6.9{sub -1.2}{sup +1.2}(stat){sub -0.7}{sup +0.8}(syst) ± 0.4 (lumi) pb. These findings are in good agreement with standard model predictions and measurements performed using other top quark decay channels.
Book Synopsis Search for T-channel Single Top Quark Production in Pp ̄collisions at 1.96 TeV by : Philip Michael Perea
Download or read book Search for T-channel Single Top Quark Production in Pp ̄collisions at 1.96 TeV written by Philip Michael Perea and published by . This book was released on 2006 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
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 Observation of Single Top Quark Production and Measurement of by :
Download or read book Observation of Single Top Quark Production and Measurement of written by and published by . This book was released on 2010 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report the observation of electroweak single top quark production in 3.2 fb−1 of p{bar p} collision data collected by the Collider Detector at Fermilab at √s = 1.96 TeV. Candidate events in the W+jets topology with a leptonically decaying W boson are classified as signal-like by four parallel analyses based on likelihood functions, matrix elements, neural networks, and boosted decision trees. These results are combined using a super discriminant analysis based on genetically evolved neural networks in order to improve the sensitivity. This combined result is further combined with that of a search for a single top quark signal in an orthogonal sample of events with missing transverse energy plus jets and no charged lepton. We observe a signal consistent with the standard model prediction but inconsistent with the background-only model by 5.0 standard deviations, with a median expected sensitivity in excess of 5.9 standard deviations. We measure a production cross section of 2.3{sub -0.5}{sup +0.6}(stat + sys) pb, extract the CKM matrix element value.
Book Synopsis Measurement of the Jet Mass in Highly Boosted T-tbar Events from Pp Collisions at $\sqrt{s}$ by :
Download or read book Measurement of the Jet Mass in Highly Boosted T-tbar Events from Pp Collisions at $\sqrt{s}$ written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The first measurement of the jet mass m[jet] of top quark jets produced in t t-bar events from pp collisions at sqrt(s) = 8 TeV is reported for the jet with the largest transverse momentum pt in highly boosted hadronic top quark decays. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 19.7 inverse femtobarns. The measurement is performed in the lepton+jets channel in which the products of the semileptonic decay t to bW with W to l nu where l is an electron or muon, are used to select t t-bar events with large Lorentz boosts. The products of the fully hadronic decay t to bW with W to q q'-bar are reconstructed using a single Cambridge-Aachen jet with distance parameter R=1.2, and pt>400 GeV. The t t-bar cross section as a function of m[jet] is unfolded at the particle level and is used to test the modelling of highly boosted top quark production. The peak position of the m[jet] distribution is sensitive to the top quark mass m[t], and the data are used to extract a value of m[t] to assess this sensitivity.
Book Synopsis Uncovering the Single Top by : Jorge Armando Benitez
Download or read book Uncovering the Single Top written by Jorge Armando Benitez and published by . This book was released on 2009 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Measurement of the Top Anti-top Quark Pair Production Cross-section in the [tau] + Jets Channel at [square Root of S] by : Teeba Rashid
Download or read book Measurement of the Top Anti-top Quark Pair Production Cross-section in the [tau] + Jets Channel at [square Root of S] written by Teeba Rashid and published by . This book was released on 2013 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurement of the Production Cross-section of a Single Top Quark in Association with a W Boson at 8 TeV with the ATLAS Experiment by :
Download or read book Measurement of the Production Cross-section of a Single Top Quark in Association with a W Boson at 8 TeV with the ATLAS Experiment written by and published by . This book was released on 2016 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cross-section for the production of a single top quark in association with a W boson in proton-proton collisions at √s = 8 is measured. The dataset corresponds to an integrated luminosity of 20.3 fb-1, collected by the ATLAS detector in 2012 at the Large Hadron Collider at CERN. Events containing two leptons and one central b-jet are selected. The Wt signal is separated from the backgrounds using boosted decision trees, each of which combines a number of discriminating variables into one classifier. Production of Wt events is observed with a significance of 7.7[sigma]. The cross-section is extracted in a profile likelihood fit to the classifier output distributions. The Wt cross-section, inclusive of decay modes, is measured to be 23.0±1.3(stat.)-3.5+3.2(syst.)±1.1(lumi.) pb. The measured cross-section is used to extract a value for the CKM matrix element.
Book Synopsis Measurements of the Top Anti-top Production Cross Section and Top Quark Mass in the Hadronically Decaying Tau + Jets Decay Channel at CDF by : Daryl Curtis Hare
Download or read book Measurements of the Top Anti-top Production Cross Section and Top Quark Mass in the Hadronically Decaying Tau + Jets Decay Channel at CDF written by Daryl Curtis Hare and published by . This book was released on 2011 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for S Channel Single Top Quark Production in Pp Collisions at $\sqrt{s}$ by :
Download or read book Search for S Channel Single Top Quark Production in Pp 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: A search is presented for single top quark production in the s channel in proton-proton collisions with the CMS detector at the CERN LHC in decay modes of the top quark containing a muon or an electron in the final state. The signal is extracted through a maximum-likelihood fit to the distribution of a multivariate discriminant defined using boosted decision trees to separate the expected signal contribution from background processes. Data collected at centre-of-mass energies of 7 and 8 TeV yield cross sections of 7.1 +/- 8.1 pb and 13.4 +/- 7.3 pb, respectively, and a best fit value of 2.0 +/- 0.9 for the combined ratio of the measured and expected values. The signal significance is 2.5 standard deviations, and the upper limit on the rate relative to the standard model expectation is 4.7 at 95% confidence level.
Book Synopsis Measurement of the Electroweak Single Top Quark Production Cross Section and the CKM Matrix Element $ by :
Download or read book Measurement of the Electroweak Single Top Quark Production Cross Section and the CKM Matrix Element $ written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The establishment of the electroweak single top quark production at CDF is experimentally challenging. The small single top signal hidden under large uncertain background processes makes it necessary an excellent understanding of the detector and a detailed study of the processes involved. Moreover, simple counting experiments are not sufficient to extract enough information from the candidate event sample and multivariate analysis techniques are crucial to distinguish signal from background. This thesis presents the world's most sensitive individual search, together with CDF's Neural Network analysis, for the combined s- and t-channel single top production. This analysis uses a dataset that corresponds to an integrated luminosity of 3.2fb-1, and is based on a Boosted Decision Tree method that combines information from several input variables to construct a final powerful discriminant, reaching a sensitivity to the combined single top quark production equivalent to 5.2[sigma]. The measured combined single top quark production cross section is 2.1+0.7 -0.6 pb assuming a top quark mass of 175 GeV/c2. The probability that this result comes from a background-only fluctuation (p-value) is 0.0002, which corresponds to 3.5[sigma].
Book Synopsis Single Top Quark Measurements at the Tevatron by :
Download or read book Single Top Quark Measurements 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: This paper reports the most recent measurements of single top quark production performed by CDF and D0 collaborations in proton-antiproton collisions at Tevatron. Events are selected in the lepton+jets final state by CDF and D0 and in the missing transverse energy plus jets final state by CDF. The small single top signal in s-channel, t-channel and inclusive s+t channel is separated from the large background by using different multivariate techniques. We also present the most recent results on extraction of the CKM matrix element $
Book Synopsis Observation of $t$-channel Electroweak Top Quark Production by :
Download or read book Observation of $t$-channel Electroweak Top Quark Production written by and published by . This book was released on 2011 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the heaviest known fundamental particle, with a mass of 172.0+0.9-1.3GeV. This is nearly twice the mass of the second heaviest known particle, the Z boson, and roughly the mass of a gold atom. Because of its unusually large mass, studying the top quark may provide insight into the Higgs mechanism and other beyond the standard model physics. Only two accelerators in the world are powerful enough to produce top quarks. The Tevatron, which first accelerated protons in 1983, has produced almost 400,000 top quarks, roughly half at each of its two detectors: DO and CDF. The LHC is a much newer accelerator which currently has accumulated about 0.5% as much data as the Tevatron. However, when running at full luminosity, the LHC is capable of producing a top quark about once every second and will quickly surpass the Tevatron as the leading producer of top quarks. This analysis uses data from the DØ detector at the Tevatron, which are described in chapter 3. Top quarks are produced most often in pairs of top and anti-top quarks through an interaction of the strong force. This production mode was first observed in 1995 at the Tevatron. However, top quarks can also be produced though an electroweak interaction, which produces just one top quark. This production mode was first observed at the Tevatron in 2008. Single top quark production can occur in different channels. In this analysis, a measurement of the cross section of the t-channel production mode is performed. This measurement uses 5.4 fb-1 of data and uses the technique of boosted decision trees in order to separate signal from background events. The t-channel cross section is measured to be: ?(p$ar{p}$ → tqb + X) = 3.03+0.78-0.66 pb (0.0.1). Additional cross section measurements were also performed for the s-channel as well as the s + t-channel. The measurement of each one of these three cross sections was repeated three times using different techniques, and all three methods were combined into a 'super-method' which achieves the best performance. The details of these additional measurements are shown in appendix A.
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