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Download or read book Measurement of the Top-quark Pair Production Cross-section in Events with Two Leptons and Bottom-quark Jets Using the Full CDF Data Set written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the Top Quark Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection and Identified B-jets written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Using 1.0 fb^{-1} of data collected by the Collider Detector at Fermilab (CDF) from Run II of the Fermilab Tevatron, we measure the top-antitop production cross-section in events with two leptons, significant missing transverse energy, and at least jets, at least one of which is identified as a b-jet. As the Run II dataset grows, more stringent tests of Standard Model predictions for the top quark sector are becoming possible. The dilepton channel, where both top quarks decay t-> W b ->l nu b, is of particular interest due to its high purity. Use of an isolated track as the second lepton significantly increases the dilepton acceptance, at the price of some increase in background, particularly from W + jets events where one of the jets is identified as a lepton. To control the increase in background we add to the event selection the requirement that at least one of the jets be identified as a b-jet, reducing the background contribution from all sources. Assuming a branching ratio of BR(W->l nu) = 10.8% and a top mass of m_top = 175 GeV/c^{2} the measured cross-section is sigma = (10.5 +/- 1.8 stat. +/- 0.8 syst. +/- 0.6 lumi.) pb.
Author : Teresa Spreitzer
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (13 download)
Download or read book Measurement of the Top Quark Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection and Identified B-jets written by Teresa Spreitzer and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the Single Top Quark Production Cross Section and written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An updated measurement of the single top quark production cross section is presented using the full data set collected by the Collider Detector at Fermilab (CDF), corresponding to 9.5 fb-1 of integrated luminosity from proton-antiproton collisions at 1.96 TeV center-of-mass energy. The events selected contain an imbalance in the total transverse momentum, jets identified as containing b quarks, and no identified leptons. The sum of the s- and t-channel single top quark cross sections is measured to be 3.53-1.16+1.25 pb and a lower limit on the magnitude of the top-to-bottom quark coupling,
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ISBN 13 :
Total Pages : 222 pages
Book Rating : 4.:/5 (953 download)
Download or read book Measurement of the Single Top Quark Cross Section in the Lepton Plus Jets Final State in Proton-Antiproton Collisions at a Center of Mass Energy of 1.96 TeV Using the CDF II Detector written by and published by . This book was released on 2012 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the single top quark cross section in the lepton plus jets final state using an integrated luminosity corresponding to 7.5 fb-1 of p\bar p collision data collected by the Collider Detector at Fermilab. The single top candidate events are identified by the signature of a charged lepton, large missing transverse energy, and two or three jets with at least one of them identified as originating from a bottom quark. A new Monte Carlo generator POWHEG is used to model the single top quark production processes, which include s-channel, t-channel, and Wt-channel. A neural network multivariate method is exploited to discriminate the single top quark signal from the comparatively large backgrounds. We measure a single top production cross section of $3.04^{+0.57}_{-0.53} (\mathrm{stat.~+~syst.})$ pb assuming $m_{\rm top}=172.5$~GeV/$c^2$. In addition, we extract the CKM matrix element value $
Author : Nabin Poudyal
Publisher :
ISBN 13 :
Total Pages : 259 pages
Book Rating : 4.:/5 (129 download)
Download or read book Measurement of the Cross Section of Top Quark Pairs Produced in Association with a Photon in Lepton + Jets Events at 8́(s written by Nabin Poudyal and published by . This book was released on 2021 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: The inclusive production cross section of top quark pairs in association with a photon is measured in proton-proton collisions at the LHC with 13 TeV energy using the full RunII data collected by CMS in 2016, 2017, and 2018 with a total corresponding integrated luminosity of 137 fb 8́21 . The relative fraction of ttÎđ events normalized to inclusive tt production is measured. The cross section measurement provides important information about the electromagnetic coupling of the standard model top quark and is sensitive to physics beyond the standard model. The analysis is carried out in the in semileptonic decay channel with a well isolated high P T lepton (electron and muon), at least four jets out of which at least one must be b-tagged, and an isolated photon. Photons may be emitted from initial state radiation, top quarks, and decay products of top quarks. A simultaneous likelihood fit of control regions with the signal region is done to constraint the backgrounds and to extract the ttÎđ cross section. The measurement of the ratio of ttÎđ to tt is 0.02055 ℗ł 0.00099 (syst.) ℗ł 0.00099 (stat.) in the e + jets channel, 0.02156 ℗ł 0.00068 (syst.) ℗ł 0.00068 (stat.) in ℗æ + jets channel, and 0.02203 ℗ł 0.00064 (syst.) ℗ł 0.00064 (stat.) in the l + jets channel. The measured inclusive cross section is 3.81 ℗ł 0.15 (syst.) ℗ł 0.10 (stat.) pb in e + jets channel, 3.87 ℗ł 0.11 (syst.) ℗ł 0.07 (stat.) pb in ℗æ + jets channel, and 3.96 ℗ł 0.10 (syst.) ℗ł 0.06 (stat.) pb in l + jets channel for full RunII data. The results are in agreement with the standard model next to leading order prediction.
Author :
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ISBN 13 :
Total Pages : 184 pages
Book Rating : 4.:/5 (727 download)
Download or read book Top Quark Pair Production Cross Section in the Lepton+jets Channel Using B-tagging at written by and published by . This book was released on 2008 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark pair production cross section measurement in the lepton+jets channel with b-tagging algorithm is described. About 900 pb−1 data collected by the D0 detector at the Fermilab Tevatron are used for this analysis. In this thesis, event selection, background estimation, and cross section calculation are discussed in detail. In addition, calibration of the Luminosity Monitor readout electronics and a new b-tagging algorithm, the SLTNN tagger, are also discussed in this thesis.
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ISBN 13 :
Total Pages : 193 pages
Book Rating : 4.:/5 (873 download)
Download or read book Measurement of the Top Quark Pair Production Cross Section in Proton-antiproton Collisions at a Center of Mass Energy of 1.96 TeV, Hadronic Top Decays with the D0 Detector written by and published by . This book was released on 2009 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: Of the six quarks in the standard model the top quark is by far the heaviest: 35 times more massive than its partner the bottom quark and more than 130 times heavier than the average of the other five quarks. Its correspondingly small decay width means it tends to decay before forming a bound state. Of all quarks, therefore, the top is the least affected by quark confinement, behaving almost as a free quark. Its large mass also makes the top quark a key player in the realm of the postulated Higgs boson, whose coupling strengths to particles are proportional to their masses. Precision measurements of particle masses for e.g. the top quark and the W boson can hereby provide indirect constraints on the Higgs boson mass. Since in the standard model top quarks couple almost exclusively to bottom quarks (t 2!Wb), top quark decays provide a window on the standard model through the direct measurement of the Cabibbo-Kobayashi-Maskawa quark mixing matrix element V{sub tb}. In the same way any lack of top quark decays into W bosons could imply the existence of decay channels beyond the standard model, for example charged Higgs bosons as expected in two-doublet Higgs models: t 2!Hb. Within the standard model top quark decays can be classified by the (lepton or quark) W boson decay products. Depending on the decay of each of the W bosons, t{bar t} pair decays can involve either no leptons at all, or one or two isolated leptons from direct W 2!e{bar {nu}}{sub e} and W 2![mu]{bar {nu}}{sub {mu}} decays. Cascade decays like b 2!Wc 2!e{bar {nu}}{sub e}c can lead to additional non-isolated leptons. The fully hadronic decay channel, in which both Ws decay into a quark-antiquark pair, has the largest branching fraction of all t{bar t} decay channels and is the only kinematically complete (i.e. neutrino-less) channel. It lacks, however, the clear isolated lepton signature and is therefore hard to distinguish from the multi-jet QCD background. It is important to measure the cross section (or branching fraction) in each channel independently to fully verify the standard model. Top quark pair production proceeds through the strong interaction, placing the scene for top quark physics at hadron colliders. This adds an additional challenge: the huge background from multi-jet QCD processes. At the Tevatron, for example, t{bar t} production is completely hidden in light q{bar q} pair production. The light (i.e. not bottom or top) quark pair production cross section is six orders of magnitude larger than that for t{bar t} production. Even including the full signature of hadronic t{bar t} decays, two b-jets and four additional jets, the QCD cross section for processes with similar signature is more than five times larger than for t{bar t} production. The presence of isolated leptons in the (semi)leptonic t{bar t} decay channels provides a clear characteristic to distinguish the t{bar t} signal from QCD background but introduces a multitude of W- and Z-related backgrounds.
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ISBN 13 :
Total Pages : 4 pages
Book Rating : 4.:/5 (871 download)
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.
Author : Robert E. Calkins
Publisher :
ISBN 13 : 9781267906960
Total Pages : 241 pages
Book Rating : 4.9/5 (69 download)
Download or read book Measurements of the Top Quark Pair Production Cross Section and Branching Ratio to a W-boson and Bottom Quark Using the Semi-leptonic and Dilepton Final States with the ATLAS Detector at the LHC written by Robert E. Calkins and published by . This book was released on 2012 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : In the Standard Model, the top quark plays a unique role as the heaviest known fundamental particle and as a quark that decays before it is able to hadronize. Top quarks are expected to decay to a W-boson and a b-quark nearly 100% of the time. If the branching ratio of t → Wb is lower than one, the distribution of the number of b-tagged jets will shift to lower multiplicities. A simultaneous likelihood fit to the number of b-tagged jets distributions in the lepton+jets and dilepton channels is performed on 4.7 fb−1 of data collected by the ATLAS detector to extract both the branching ratio and the tt ̄ cross section. The branching ratio of t → Wb, R, is measured to be 1.06±0.11, which is consistent with the Standard Model value. This is the first measurement of the t → Wb branching ratio performed with the ATLAS detector using both the lepton+jets and dilepton channels at the LHC. The tt ̄ cross section is measured to be [special characters omitted] pb, which agrees with NNLO predictions.
Author : S. Cabrera
Publisher :
ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (316 download)
Download or read book Top Pair Production Cross Section at S**(1/2) written by S. Cabrera and published by . This book was released on 2006 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Possible effects from physics beyond the Standard Model have been investigated in top quark decays from a data sample enriched in t{bar t} events produced in p{bar p} collisions at {radical}s = 1.96 TeV with an integrated luminosity of approximately 700 pb{sup -1} and collected with the CDF II detector. The combined t{bar t} production cross section measurement 7.3 {+-} 0.9 pb agrees with the QCD NLO predictions: 6.7 {+-} 0.8 pb assuming m{sub top} = 175 GeV/c{sup 2}. The fraction of the V + A current in top quark decay, f{sub V+A}, is determined using the invariant mass of the charged lepton and the bottom quark jet in the decay chain t {yields} Wb {yields} {ell}{nu}b (where {ell} = e or {mu}). The measured value f{sub V+A} = - 0.06 {+-} 0.25 under the assumption m{sub top} = 175 GeV/c{sup 2} is in agreement with the Standard Model. They set an upper limit on f{sub V+A} of 0.29 at the 95% confidence level.
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ISBN 13 :
Total Pages : 4 pages
Book Rating : 4.:/5 (16 download)
Download or read book Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S**ư 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.
Author :
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ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (16 download)
Download or read book Top Pair Production Cross Section at S**ư written by and published by . This book was released on 2006 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Possible effects from physics beyond the Standard Model have been investigated in top quark decays from a data sample enriched in t{bar t} events produced in p{bar p} collisions at √s = 1.96 TeV with an integrated luminosity of approximately 700 pb−1 and collected with the CDF II detector. The combined t{bar t} production cross section measurement 7.3 ± 0.9 pb agrees with the QCD NLO predictions: 6.7 ± 0.8 pb assuming m{sub top} = 175 GeV/c2. The fraction of the V + A current in top quark decay, f{sub V+A}, is determined using the invariant mass of the charged lepton and the bottom quark jet in the decay chain t → Wb → l?b (where l = e or?). The measured value f{sub V+A} = - 0.06 ± 0.25 under the assumption m{sub top} = 175 GeV/c2 is in agreement with the Standard Model. They set an upper limit on f{sub V+A} of 0.29 at the 95% confidence level.
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ISBN 13 :
Total Pages : 26 pages
Book Rating : 4.:/5 (16 download)
Download or read book First Measurement of the Cross Section for Top-Quark Pair Production in Proton-Proton Collisions at $\sqrt{s} written by and published by . This book was released on 2011 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first measurement of the cross section for top-quark pair production in pp collisions at the LHC at center-of-mass energy sqrt(s)= 7 TeV has been performed using 3.1 {\pm} 0.3 inverse pb of data recorded by the CMS detector. This result utilizes the final state with two isolated, highly energetic charged leptons, large missing transverse energy, and two or more jets. Backgrounds from Drell-Yan and non-W/Z boson production are estimated from data. Eleven events are observed in the data with 2.1 {\pm} 1.0 events expected from background. The measured cross section is 194 {\pm} 72 (stat.) {\pm} 24 (syst.) {\pm} 21 (lumi.) pb, consistent with next-to-leading order predictions.
Download or read book Measurement of the Top Pair Production Cross Section at CDF Using Neural Networks written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the Tevatron accelerator at Fermilab protons and antiprotons are collided at a 1.96 TeV center of mass energy. CDF and D0 are the two experiments currently operating at the Tevatron. At these energies top quark is mostly produced via strong interactions as a top anti-top pair (t[bar t]). The top quark has an extremely short lifetime and according to the Standard Model it decays with [approx]100% probability into a b quark and a W boson. In the ''lepton+jets'' channel, the signal from top pair production is detected for those events where one of the two W bosons decays hadronically in two quarks which they see as jets in the detector, and the other W decays into an electrically charged lepton and a neutrino. A relatively unambiguous identification in the detector is possible when they require that the charged lepton must be an electron or muon of either charge. The neutrino does not interact in the detector and its presence is inferred from an imbalance in the transverse energy of the event. They present a measurement of the top pair production cross section in p[bar p] collisions at 1.96 TeV, from a data sample collected at CDF between March 2002 and September 2003 with an integrated luminosity of 193.5 pb[sup -1]. In order to bring the signal to background ratio at manageable levels, measurements in this channel traditionally use precision tracking information to identify at least one secondary vertex produced in the decay of a long lived b hadron. A different approach is taken here. Because of the large mass of the top quark, t[bar t] events tend to be more spherical and more energetic than most of the background processes which otherwise mimic the t[bar t] signature in the ''lepton+jets'' channel. A number of energy based and event shape variables can be used to statistically discriminate between signal and background events. Monte Carlo simulation is used to model the kinematics of t[bar t] and most of the background processes. A neural network technique is employed to combine multiple variables in order to enhance signal versus background separation. Such a measurement takes advantage of a larger data sample than the b-tagging based analyses and achieves a comparable level of precision. A binned likelihood fit to the neutral network output distribution for a 519 events data sample yields a 17.6 [+-] 3.0(stat)% fraction of t[bar t] events. The inclusive top pair production cross section is measured to be [sigma][sub t[bar t]] = 6.6[+-]1.1(stat)[+-]1.5(syst) pb.
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ISBN 13 :
Total Pages : 194 pages
Book Rating : 4.:/5 (16 download)
Download or read book Measurement of the Top Quark Mass at CDF II. written by and published by . This book was released on 2005 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors describe a measurement of the top quark mass using events with two charged leptons collected by the CDF II Detector from p$ar{p}$ collisions with √s = 1.96 TeV at the Fermilab Tevatron. The posterior probability distribution of the top quark pole mass is calculated using the differential cross-section for the t$ar{t}$ production and decay expressed with respect to observed leptons and jets momenta. The presence of background events in the collected sample is modeled using calculations of the differential cross-sections for major background processes. This measurement represents the first application of this method to events with two charged leptons. In a data sample with integrated luminosity of 340 pb-1, they observe 33 candidate events and measure Mtop = 165.2 ± 61.stat ± 3.4syst GeV/c2.
Author : Andrew N. Kovalev
Publisher :
ISBN 13 :
Total Pages : 176 pages
Book Rating : 4.:/5 (244 download)
Download or read book Measurement of the Top Quark Mass at CDF II written by Andrew N. Kovalev and published by . This book was released on 2005 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
