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Top Quark Decay Kinematics In Fully Reconstructed Tt Events In The E Or Mu Et Greater Than Or Equal To 4 Jet Decay Channel
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Book Synopsis Top Quark Decay Kinematics in Fully Reconstructed Tt̄ Events in the E Or [mu] + EṮ + [greater Than Or Equal To] 4 Jet Decay Channel by : Eugene Hall Guillian
Download or read book Top Quark Decay Kinematics in Fully Reconstructed Tt̄ Events in the E Or [mu] + EṮ + [greater Than Or Equal To] 4 Jet Decay Channel written by Eugene Hall Guillian and published by . This book was released on 1999 with total page 852 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Top Quark Mass in Events with Two Charged Leptons at the D0 Experiment by : Daniel Boline
Download or read book Top Quark Mass in Events with Two Charged Leptons at the D0 Experiment written by Daniel Boline and published by . This book was released on 2010 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The top quark is the most massive observed fundamental subatomic particle, and at the Tevatron accelerator is produced mostly in top-antitop ( tt ) quark pairs from the collisions of protons and anti-protons. Each top quark decays into a bottom quark and a W boson. The W boson can then decay into a pair of quarks, or into a charged lepton and a neutrino. The various decays can be broken up into three different channels based on the number of leptons from the decay of the W bosons: all-jets (with no leptons), lepton+jets (with one lepton), and dilepton (with two leptons). This dissertation will present a measurement of the top quark mass in the dilepton channel. The dilepton channel is characterized by two leptons, two neutrinos and two b-quarks. The neutrinos are not directly observed, but their absence is felt as missing transverse momentum ([Special characters omitted.] ) in the detector. The combination of two leptons and large [Special characters omitted.] produces an easily isolated signal, giving the dilepton channel a high signal over background ratio. Having two neutrinos means that we cannot know what the transverse momenta of either neutrino is. This means that even if we knew the momenta of the leptons and b-quarks perfectly, we would be unable to reconstruct the mass of the top quark. This measurement gets around this problem by scanning over all possible values of the top mass, finding all consistent tt combinations, assigning a kinematic weight to each, and then adding the weights for each combination at a given possible top mass. The lepton momenta, jet momenta, and [Special characters omitted.] are only known to within some finite precision, so for a given top mass, I also vary each of these momenta within their resolutions and add the weights for a given possible top mass. After scanning over possible top masses, I choose the top mass with the largest sum of weights [Special characters omitted.] as an observable for the event. I then perform a template based likelihood fit of m t using [Special characters omitted.] . I analyze 322 candidate events collected by the DØ detector, and obtain a top quark mass of: [Special characters omitted.]
Book Synopsis Top Quark Mass in Events with Two Charged Leptons at the D0 Experiment by :
Download or read book Top Quark Mass in Events with Two Charged Leptons at the D0 Experiment written by and published by . This book was released on 2010 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the most massive observed fundamental subatomic particle, and at the Tevatron accelerator is produced mostly in top-antitop (t{bar t}) quark pairs from the collisions of protons and anti-protons. Each top quark decays into a bottom quark and a W boson. The W boson can then decay into a pair of quarks, or into a charged lepton and a neutrino. The various decays can be broken up into three different channels based on the number of leptons from the decay of the W bosons: all-jets (with no leptons), lepton+jets (with one lepton), and dilepton (with two leptons). This dissertation will present a measurement of the top quark mass in the dilepton channel. The dilepton channel is characterized by two leptons, two neutrinos and two b-quarks. The neutrinos are not directly observed, but their absence is felt as missing transverse momentum (p{sub T}) in the detector. The combination of two leptons and large p{sub T} produces an easily isolated signal, giving the dilepton channel a high signal over background ratio. Having two neutrinos means that we cannot know what the transverse momenta of either neutrino is. This means that even if we knew the momenta of the leptons and b-quarks perfectly, we would be unable to reconstruct the mass of the top quark. This measurement gets around this problem by scanning over all possible values of the top mass, finding all consistent t{bar t} combinations, assigning a kinematic weight to each, and then adding the weights for each combination at a given possible top mass. The lepton momenta, jet momenta, and p{sub T} are only known to within some finite precision, so for a given top mass, I also vary each of these momenta within their resolutions and add the weights for a given possible top mass. After scanning over possible top masses, I choose the top mass with the largest sum of weights m{sub t}{sup max} as an observable for the event. I then perform a template based likelihood fit of m{sub t} using m{sub t}{sup max}. I analyze 322 candidate events collected by the D0 detector, and obtain a top quark mass of: m{sub t} = 174.8 ± 3.1 GeV.
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 The Large Hadron Collider by : Thomas Schörner-Sadenius
Download or read book The Large Hadron Collider written by Thomas Schörner-Sadenius and published by Springer. This book was released on 2015-05-15 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive volume summarizes and structures the multitude of results obtained at the LHC in its first running period and draws the grand picture of today’s physics at a hadron collider. Topics covered are Standard Model measurements, Higgs and top-quark physics, flavour physics, heavy-ion physics, and searches for supersymmetry and other extensions of the Standard Model. Emphasis is placed on overview and presentation of the lessons learned. Chapters on detectors and the LHC machine and a thorough outlook into the future complement the book. The individual chapters are written by teams of expert authors working at the forefront of LHC research.
Book Synopsis Measurements of the Top-quark Decay Width and Mass at CDF Using the Template Method by :
Download or read book Measurements of the Top-quark Decay Width and Mass at CDF Using the Template Method written by and published by . This book was released on 2012 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements of the top quark decay width and mass are presented using the tt events produced in p p collisions at Fermilab's Tevatron collider and collected by the CDF II detector. A data sample corresponding to 4.3 fb-1 of integrated luminosity is used for the top quark width measurement. Two estimators, the reconstructed top quark mass and the mass of hadronically decaying W boson that comes from the top-quark decay are reconstructed for each event and compared with templates of different input top quark widths and deviations from nominal CDF jet energy scale ([Delta]JES) to perform a simultaneous fit for both parameters. [Delta]JES is used for the in situ calibration of the jet energy scale at CDF. By applying a Feldman-Cousins limit-setting approach, we establish an upper limit at 95% confidence level (CL) of [Gamma]top
Book Synopsis Kinematics of Top Decays from CDF. by :
Download or read book Kinematics of Top Decays from 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 study of the kinematics Of W+[ge] 3 jet events produced in p[bar p] collisions at[radical]s= 1.8 TeV. We describe several techniques used to compare the observed events with expectations both from direct W+ jets production and from production and decay of heavy top quark pairs. We also study the kinematic features of the events used to measure the top mass. Finally we show the results obtained looking for top candidates in the channel with 6 jets in the final state.
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 :
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 and published by . This book was released on 2011 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, we present the first exclusive observation of the t-t → hadronic [tau] + jets decay channel. Using these events, we measure the t-t pair production cross section and the top quark mass in 2.2 fb-1 of data collected with the Collider Detector at Fermilab (CDF). The Tevatron accelerator at Fermilab provides collisions of protons and anti-protons at a center-of-mass energy of √s = 1.96 TeV and is one of only two accelerators in the world with enough energy to produce top quarks. With a branching fraction of nearly 10%, the hadronic [tau] + jets decay channel is the third largest t-t decay mode, and it has only been minimally explored. This the first measurement of the t-t pair production cross section in this decay channel at CDF and the first measurement of the top quark mass in this decay channel in the world. The analysis introduces a new method to recover the total momentum of the [nu] produced in the [tau] decay and an artificial neural network to reduce the contribution from the largest background source, QCD multijet background. The t-t pair production cross section is extracted by minimizing a negative log likelihood function which compares the number of observed events to the number of expected events for a given t-t cross section. The top quark mass is extracted by minimizing a negative log likelihood function built from signal and ii background probabilities which are based on the matrix elements for t-t production and decay and W + 4 parton production, respectively. Using events selected with exactly 1 hadronically decaying [tau], exactly 4 jets with at least 1 identified as having originated from a b quark, and large missing transverse energy, we measure the t-t pair production cross section to be 8.8 ± 3.3 (stat.) ± 2.2 (syst.) pb and the top quark mass to be 172.7±9.3 (stat.) ±3.7 (syst.) GeV. We find both values to be in good agreement with previous measurements in other t-t decay channels, and the cross section to be consistent with next-to-leading order theoretical predictions.
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 Higgs Boson Decays into a Pair of Bottom Quarks by : Cecilia Tosciri
Download or read book Higgs Boson Decays into a Pair of Bottom Quarks written by Cecilia Tosciri and published by Springer Nature. This book was released on 2021-10-22 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery in 2012 of the Higgs boson at the Large Hadron Collider (LHC) represents a milestone for the Standard Model (SM) of particle physics. Most of the SM Higgs production and decay rates have been measured at the LHC with increased precision. However, despite its experimental success, the SM is known to be only an effective manifestation of a more fundamental description of nature. The scientific research at the LHC is strongly focused on extending the SM by searching, directly or indirectly, for indications of New Physics. The extensive physics program requires increasingly advanced computational and algorithmic techniques. In the last decades, Machine Learning (ML) methods have made a prominent appearance in the field of particle physics, and promise to address many challenges faced by the LHC. This thesis presents the analysis that led to the observation of the SM Higgs boson decay into pairs of bottom quarks. The analysis exploits the production of a Higgs boson associated with a vector boson whose signatures enable efficient triggering and powerful background reduction. The main strategy to maximise the signal sensitivity is based on a multivariate approach. The analysis is performed on a dataset corresponding to a luminosity of 79.8/fb collected by the ATLAS experiment during Run-2 at a centre-of-mass energy of 13 TeV. An excess of events over the expected background is found with an observed (expected) significance of 4.9 (4.3) standard deviation. A combination with results from other \Hbb searches provides an observed (expected) significance of 5.4 (5.5). The corresponding ratio between the signal yield and the SM expectation is 1.01 +- 0.12 (stat.)+ 0.16-0.15(syst.). The 'observation' analysis was further extended to provide a finer interpretation of the V H(H → bb) signal measurement. The cross sections for the VH production times the H → bb branching ratio have been measured in exclusive regions of phase space. These measurements are used to search for possible deviations from the SM with an effective field theory approach, based on anomalous couplings of the Higgs boson. The results of the cross-section measurements, as well as the constraining of the operators that affect the couplings of the Higgs boson to the vector boson and the bottom quarks, have been documented and discussed in this thesis. This thesis also describes a novel technique for the fast simulation of the forward calorimeter response, based on similarity search methods. Such techniques constitute a branch of ML and include clustering and indexing methods that enable quick and efficient searches for vectors similar to each other. The new simulation approach provides optimal results in terms of detector resolution response and reduces the computational requirements of a standard particles simulation.
Book Synopsis Top-quark Mass Measurement Using Events with Missing Transverse Energy and Jets at CDF. by :
Download or read book Top-quark Mass Measurement Using Events with Missing Transverse Energy and Jets at CDF. written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the top-quark mass with tt events using a data sample corresponding to an integrated luminosity of 5.7 fb -1 of pp collisions at the Fermilab Tevatron with √s = 1.96 TeV and collected by the CDF II Detector. We select events having no identified charged leptons, large missing transverse energy, and four, five, or six jets with at least one jet containing a secondary vertex consistent with the decay of a b quark. This analysis considers events from the semileptonic tt decay channel, including events that contain tau leptons, which are usually not included in the top-quark mass measurements. The measurement uses as kinematic variables the invariant mass of two jets consistent with the mass of the W boson, and the invariant masses of two different three-jet combinations. We fit the data to signal templates of varying top-quark masses and background templates, and measure a top-quark mass of Mtop = 172.3 ± 2.4 (stat) ± 1.0 (syst) GeV/c2.
Download or read book Observation of the Top Quark written by and published by . This book was released on 1995 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The D0 collaboration reports on a search for the Standard Model top quark in p{bar p} collisions at (square root)s = 1.8 TeV at the Fermilab Tevatron, with an integrated luminosity of approximately 50 pb−1. We have searched for t{bar t} production in the dilepton and single lepton decay channels, with and without tagging of b quark jets. We observe 17 events with an expected background of 3.8 " 0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2 x 10−6 (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 19921{sup +19} (stat.) "22 (syst.) GeV/c2 and its production cross section to be 6.4 " 2.2 pb.
Book Synopsis Physics of the Top Quark at D0 New Measurement of the Production Cross Section and Mass by :
Download or read book Physics of the Top Quark at D0 New Measurement of the Production Cross Section and Mass 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 measurement of the t[anti t] production cross section in p[anti p] collisions at[radical]s= 1.8 TeV and a measurement of top quark mass m[sub t] by the D0 experiment at the Fermilab Tevatron. The measurements are based on the data from the 1992- 1996 run during which the D0 detector was exposed to the integrated luminosity of approximately 125 pb[sup -1]. We observe 39 t[anti t] candidate events in the dilepton and lepton+jets decay channels with an expected background of 13.7[+-] 2.2 events. We measure the top quark mass m[sub t] using a two constraint fit to m[sub t] in t[anti t][yields] bW[sup+][anti b]W[sup -] final states with one W decaying to q[anti q] and the other to e[nu] or[mu][nu]. Events are binned in the fit mass versus a measure of probability for events to be the signal rather than a background. Likelihood fits to the data yield m[sub t]= 173.3[+-] 5.6 (stat)[+-] 6.2 (syst) GeV/c[sup 2]. For this mass we measure the t[anti t] production cross section to be 5.5[+-] 1.8 pb.
Book Synopsis Direct Top Quark Decay Width Measurement in the Tt̄ Lepton+Jets Channel at √s by : Philipp Stolte-Cord to Krax
Download or read book Direct Top Quark Decay Width Measurement in the Tt̄ Lepton+Jets Channel at √s written by Philipp Stolte-Cord to Krax and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark t plays an essential role in the field of elementary particle physics - in particular due to its exceptional properties comprising a large mass, which approximately equals the mass of a tungsten atom, and an enormously short lifetime. This thesis is devoted to the study of a fundamental property of the top quark - its decay width. Its value is predicted by the established Standard Model of particle physics and deviations may hint at yet unknown physics beyond this model. A direct measurement of the decay width of the top quark is presented. The analysis is based on tt events i...
Book Synopsis Reconstructing $t\bar{t}$ Events with One Lost Jet by :
Download or read book Reconstructing $t\bar{t}$ Events with One Lost Jet written by and published by . This book was released on 2015 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a technique for reconstructing the kinematics of pair-produced top quarks that decay to a charged lepton, a neutrino and four final state quarks in the subset of events where only three jets are reconstructed. We present a figure of merit that allows for a fair comparison of reconstruction algorithms without requiring their calibration. As a result, the new reconstruction of events with only three jets is fully competitive with the full reconstruction typically used for four-jet events.
Book Synopsis A Measurement of the Mass of the Top Quark in Lepton + Jets Events at CDF by : Erik Matthews Brubaker
Download or read book A Measurement of the Mass of the Top Quark in Lepton + Jets Events at CDF written by Erik Matthews Brubaker and published by . This book was released on 2004 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Precision Measurements of the Top Quark Mass and Width with the D0 Detector by :
Download or read book Precision Measurements of the Top Quark Mass and Width with the D0 Detector written by and published by . This book was released on 2010 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the discovery of the top quark in 1995 at the Fermliab Tevatron Collider, top quark properties have been measured with ever higher precision. In this article, recent measurements of the top quark mass and its width using up to 3.6 fb−1 of D0 data are summarized. Different techniques and final states have been examined and no deviations within these measurements have been observed. In addition to the direct measurements, a measurement of the top quark mass from its production cross section and a measurement of the top-antitop quark mass difference are discussed. With a mass of 173.3 ± 1.1 GeV, the top quark is the heaviest of all known fundamental particles. Due to the high mass, its Yukawa coupling is close to unity suggesting that it may play a special role in electroweak symmetry breaking. Precise measurements of both, the W boson and the top quark mass, constrain the mass of the yet unobserved Higgs boson and allow to restrict certain extensions of the Standard Model. At the Tevatron collider with a center-of-mass energy of 1.96 TeV, 85% of the top quark pairs are produced in quark-antiquark annihilation; 15% originate from gluon fusion. Top quarks are predicted to decay almost exclusively to a W boson and a bottom quark. According to the number of hadronic W decays, top events are classified into all-jets, lepton+jets and dilepton events. The lepton+jets channel is characterized by four jets, one isolated, energetic charged lepton and missing transverse energy. With 30%, the branching fraction of the lepton+jets channel is about seven times larger than the one of the dilepton channel whereas the signal to background ratio is about three times smaller. The main background in this final state comes from W +jets events. Instrumental background arises from events in which a jet is misidentified as an electron and events with heavy hadrons that decay into leptons which pass the isolation requirements. The topology of the dilepton channel is described by two jets, two isolated, energetic charged leptons and significant missing transverse energy from the undetected neutrinos. The main background are Z + jets and diboson events (WW/WZ/ZZ+jets) as well as instrumental background as characterized above. At the D0 experiment, different techniques are used to measure the top quark mass. They are summarized in the following sections together with the first measurement of the top anti-top quark mass difference and the first precise determination of the top quark width.
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