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Measurement Of Wz Production And Searches For Anomalous Top Quark Decays And Higgs Boson Production Using Tri Lepton Final States In Pbarp Collisions At Sqrts
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Book Synopsis Measurement of $WZ$ Production and Searches for Anomalous Top Quark Decays and Higgs Boson Production Using Tri-lepton Final States in $p\bar{p}$ Collisions at $\sqrt{s} by :
Download or read book Measurement of $WZ$ Production and Searches for Anomalous Top Quark Decays and Higgs Boson Production Using Tri-lepton Final States in $p\bar{p}$ Collisions at $\sqrt{s} written by and published by . This book was released on 2012 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the results of three analyses; a $WZ$ production cross section measurement, a search for new physics in anomalous top quark decays, and the search for the standard model Higgs boson, all with final states of three or more leptons -- either electrons or muons -- plus an imbalance of transverse momentum using Tevatron proton and anti-proton collisions at a center--of--mass energy of $\sqrt{s}$ = 1.96 TeV with the D0 detector at the Fermi National Accelerator Laboratory in Chicago, IL. The first analysis reports a measurement of the $WZ \rightarrow \ell^{\prime}\nu\ell\bar{\ell}$ cross section. Using 4.1 $fb^{-1}$ of integrated luminosity, we measure a cross section of 3.90$_{-0.85}^{+1.01}$($stat+syst$) $\pm$ 0.31($lumi$) pb, which is found to be in good agreement with the standard model prediction. The second analysis is an extension of the first, in which we use the same dataset and look for the flavor changing neutral current decay of $t \rightarrow Zq$ in $p\bar {p} \rightarrow t\bar{t} \rightarrow WbZq \rightarrow \ell^{\prime}\nu\ell\bar{\ell} + \rm{jets}$ decays. Here $q$ is considered to be either a $u$ or $c$ quark, and both the $q$ and $b$ quarks decay hadronically. We find no evidence of flavor changing neutral current production and set upper limits on the branching ratio of $BR(t \rightarrow Zq)
Book Synopsis Measurement of Top Quark-antiquark Pair Production in Association with a Z Boson with a Trilepton Final State in Pp Collisions at 8 TeV Center of Mass Energy by : Ian Christopher MacNeill
Download or read book Measurement of Top Quark-antiquark Pair Production in Association with a Z Boson with a Trilepton Final State in Pp Collisions at 8 TeV Center of Mass Energy written by Ian Christopher MacNeill and published by . This book was released on 2015 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for Z boson production with associated top-antitop pairs is performed with a final state which contains trileptons and b-tagged jets. The measurement is performed on the complete dataset of pp collisions at a center-of-mass energy of 8 TeV collected at the CMS detector, for a total instantaneous luminosity of 19.5 fb−1. A cross section is calculated for this final state and compared to the standard model prediction. The cross section for tt̄Z production is measured to be sigma=194+105/−89 fb. The measured cross section to theoretical cross section ratio is 0.94+0̇̇̇·51/−43. The process is measured with a significance of 2.33. This measurement is then combined with an outside 4 lepton channel measurement for an equivalent cross section measurement of sigma=200+90/−76 fb and a significance of 3.1.
Book Synopsis Measurement of the W Boson Helicity Fractions in the Decays of Top Quark Pairs to Lepton+jets Final States Produced in Pp Collisions at Sqrt(s) by :
Download or read book Measurement of the W Boson Helicity Fractions in the Decays of Top Quark Pairs to Lepton+jets Final States Produced 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: The W boson helicity fractions from top quark decays in t-tbar events are measured using data from proton-proton collisions at a centre-of-mass energy of 8 TeV. The data were collected in 2012 with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 inverse-femtobarns. Events are reconstructed with either one muon or one electron, along with four jets in the final state, with two of the jets being identified as originating from b quarks. The measured helicity fractions from both channels are combined, yielding F[0] = 0.681 +/- 0.012 (stat) +/- 0.023 (syst), F[L] = 0.323 +/- 0.008 (stat) +/- 0.014 (syst), and F[R] = -0.004 +/- 0.005 (stat) +/- 0.014 (syst) for the longitudinal, left-, and right-handed components of the helicity, respectively. These measurements of the W boson helicity fractions are the most accurate to date and they agree with the predictions from the standard model.
Book Synopsis Seeing a Single Top Quark by : Harish Potti
Download or read book Seeing a Single Top Quark written by Harish Potti and published by . This book was released on 2020 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the heaviest known elementary particle. With a coupling to the Higgs boson close to unity, the top quark plays a special role in electroweak symmetry breaking as well as in physics beyond the Standard Model. An accurate measurement of its properties can provide key information for understanding the physics at the TeV scale. In this dissertation, two measurements of the top quark properties are presented. The first part of this dissertation presents the first-ever ATLAS search for the associated production of a single top quark and a photon. This analysis is performed with 139 fb−1 of pp collision data collected by the ATLAS detector at the LHC at [square root symbol] s = 13 TeV. Only final states with exactly one lepton and at least one photon are considered in this analysis. In the second part, results from the combination of ATLAS searches for flavor changing neutral currents (FCNC) in t->Hq decays are presented. Four FCNC analyses, probing different Higgs decay modes, performed with 36.1 fb−1 of proton-proton collision data collected by the ATLAS detector in 2015-2016 are considered in the combination. They search for top-quark pair events in which one top quark decays into Wb and the other top quark decay into Hq
Book Synopsis Measurement of the W-boson Helicity in Top-quark Decays from $t\bar{t}$ Production in Lepton+jets Events in Pp Collisions at $\sqrt{s} by :
Download or read book Measurement of the W-boson Helicity in Top-quark Decays from $t\bar{t}$ Production in Lepton+jets Events in Pp Collisions at $\sqrt{s} written by and published by . This book was released on 2013 with total page 45 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.
Book Synopsis Search for New Phenomena with Top Quark Pairs in Final States with One Lepton, Jets, and Missing Transverse Momentum in Pp Collisions at [square Root]s by : ATLAS Collaboration CERN
Download or read book Search for New Phenomena with Top Quark Pairs in Final States with One Lepton, Jets, and Missing Transverse Momentum in Pp Collisions at [square Root]s written by ATLAS Collaboration CERN and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A search for new phenomena with top quark pairs in final states with one isolated electron or muon, multiple jets, and large missing transverse momentum is performed. Signal regions are designed to search for two-, three-, and four-body decays of the directly pair-produced supersymmetric partner of the top quark (stop). Additional signal regions are designed specifically to search for spin-0 mediators that are produced in association with a pair of top quarks and decay into a pair of dark-matter particles. The search is performed using the Large Hadron Collider proton-proton collision dataset at a centre-of-mass energy of s√ = 13 TeV recorded by the ATLAS detector from 2015 to 2018, corresponding to an integrated luminosity of 139 fb−1. No significant excess above the Standard Model background is observed, and limits at 95% confidence level are set in the stop-neutralino mass plane and as a function of the mediator mass or the dark-matter particle mass. Stops are excluded up to 1200 GeV (710 GeV) in the two-body (three-body) decay scenario. In the four-body scenario stops up to 640 GeV are excluded for a stop-neutralino mass difference of 60 GeV. Scalar and pseudoscalar dark-matter mediators are excluded up to 200 GeV when the coupling strengths of the mediator to Standard Model and dark-matter particles are both equal to one and when the mass of the dark-matter particle is 1 GeV
Book Synopsis 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 by : Robert E. Calkins
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.
Book Synopsis Search for Single Production of a Heavy Vector-like T Quark Decaying to a Higgs Boson and a Top Quark with a Lepton and Jets in the Final State by :
Download or read book Search for Single Production of a Heavy Vector-like T Quark Decaying to a Higgs Boson and a Top Quark with a Lepton and Jets in the Final State written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurements of ZH and WH Production in the H → Bb Decay Channel in Pp Collisions at 13 TeV with the ATLAS Detector by : ATLAS Collaboration CERN
Download or read book Measurements of ZH and WH Production in the H → Bb Decay Channel in Pp Collisions at 13 TeV with the ATLAS Detector written by ATLAS Collaboration CERN and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Measurements are presented of the Standard Model Higgs boson decaying into a bb ̄ pair and produced in association with a W or Z boson decaying into leptons, using proton-proton collision data collected between 2015 and 2018 by the ATLAS detector. The measurements use data delivered by the Large Hadron Collider at a centre-of-mass energy of s√=13 TeV, corresponding to an integrated luminosity of 139 fb−1. The production of a Higgs boson in association with a W or Z boson is established, with observed (expected) significances of 4.0 (4.1) and 5.3 (5.1) standard deviations, respectively. Cross-sections of associated production of a Higgs boson decaying into bottom quark pairs with an electroweak gauge boson, W or Z, decaying into leptons are measured as a function of the gauge boson transverse momentum in kinematic fiducial volumes. The cross-section measurements are all consistent with the Standard Model expectations, and the total uncertainties vary from 30% in the high gauge boson transverse momentum regions to 85% in the low regions
Book Synopsis Measurements of the Top Quark Pair Production Cross Section in Lepton + Jets Final States Using a Topological Multivariate Technique as Well as Lifetime B-Tagging in Proton - Anti-proton Collisions at S**(1/2) by :
Download or read book Measurements of the Top Quark Pair Production Cross Section in Lepton + Jets Final States Using a Topological Multivariate Technique as Well as Lifetime B-Tagging in Proton - Anti-proton Collisions at S**(1/2) written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract Not Provided.
Book Synopsis Measurements of the Top Quark Pair Production Cross Section in Lepton+jets Final States Using a Topological Multivariate Technique as Well as Lifetime B-tagging in Proton-antiproton Collisions at [root] by : Tobias Golling
Download or read book Measurements of the Top Quark Pair Production Cross Section in Lepton+jets Final States Using a Topological Multivariate Technique as Well as Lifetime B-tagging in Proton-antiproton Collisions at [root] written by Tobias Golling and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Evidence for WZ Production and a Measurement of the WZ Production Cross Section by :
Download or read book Evidence for WZ Production and a Measurement of the WZ Production Cross Section written by and published by . This book was released on 2007 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes a test of the Standard Model (SM) of particle physics by measuring the probability, or cross section, of simultaneously producing a W boson and a Z boson from proton-antiproton collisions. The SM predicts the cross section of WZ production to be 3.68 ± 0.25 pb. The SM and physics of WZ production are described in Chapter 2 of this dissertation. The 1.96 TeV center-of-mass energy proton-antiproton collisions are provided by the Fermi National Accelerator Laboratory (FNAL) Tevatron Collider. The W and Z particles are detected using the D0 detector, which is described in Chapter 3. The data were collected by the detector during 2002-2006 corresponding to 1 fb−1 of p{bar p} collisions. This data set is described in Chapter 6. The measurement uses the trilepton (e[nu]ee, [mu][nu]ee, e[nu][mu][mu], and [mu][nu][mu][mu]) decay channels, in which a W decays to a charged lepton plus a neutrino and a Z decays to a pair of charged leptons. The W and Z particle selection criteria, detection efficiency, and background determination are described in Chapter 7. We observe 13 candidate events in 1 fb−1 of p{bar p} collisions. In this data set we expect to see 4.5 ± 0.6 background events, and we expect to see 9.2 ± 1.0 signal events. The probability of 4.5 ± 0.6 background events to fluctuate to 13 or more events is 1.2 x 10−3 which is a 3.0 [sigma] deviation from the background estimate. A log likelihood method is used to determine the most likely cross section as determined by the measured signal efficiencies, the expected backgrounds, and the observed data. Presented in Chapter 8 is a measurement of the cross section for p{bar p} → WZ + X at √s = 1.96 TeV. The WZ diboson production cross section is measured to be [sigma]{sub WZ} = 2.7{sub -1.3}{sup +1.7} pb. This is in agreement with the predicted Standard Model cross section.
Book Synopsis Search for W' $\to $ Tb Decays in the Lepton + Jets Final State in Pp Collisions at $\sqrt{s}$ by :
Download or read book Search for W' $\to $ Tb Decays in the Lepton + Jets Final State in Pp Collisions at $\sqrt{s}$ written by and published by . This book was released on 2014 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented from a search for the production of a heavy gauge boson W' decaying into a top and a bottom quark, using a data set collected by the CMS experiment at sqrt(s) = 8 TeV and corresponding to an integrated luminosity of 19.5 inverse femtobarns. Various models of W'-boson production are studied by allowing for an arbitrary combination of left- and right-handed couplings. The analysis is based on the detection of events with a lepton (e, mu), jets, and missing transverse energy in the final state. No evidence for W'-boson production is found and 95% confidence level upper limits on the production cross section times branching fraction are obtained. For W' bosons with purely right-handed couplings, and for those with left-handed couplings assuming no interference effects, the observed 95% confidence level limit is M(W')> 2.05 TeV. For W' bosons with purely left-handed couplings, including interference effects, the observed 95% confidence level limit is M(W')> 1.84 TeV. The results presented in this paper are the most stringent limits published to date.
Book Synopsis Study of Top-Quark Production and Decays Involving a Tau Lepton at CDF and Limits on a Charged-Higgs Boson Contribution by :
Download or read book Study of Top-Quark Production and Decays Involving a Tau Lepton at CDF and Limits on a Charged-Higgs Boson Contribution written by and published by . This book was released on 2014 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for Vector-like T Quarks Decaying to Top Quarks and Higgs Bosons in the All-hadronic Channel Using Jet Substructure by :
Download or read book Search for Vector-like T Quarks Decaying to Top Quarks and Higgs Bosons in the All-hadronic Channel Using Jet Substructure written by and published by . This book was released on 2015 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is performed for a vector-like heavy T quark that is produced in pairs and that decays to a top quark and a Higgs boson. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector in proton-proton collisions at √s = 8 TeV. For T quarks with large mass values the top quarks and Higgs bosons can have significant Lorentz boosts, so that their individual decay products often overlap and merge. Methods are applied to resolve the substructure of such merged jets. Upper limits on the production cross section of a T quark with mass between 500 and 1000 GeV/c2 are derived. If the T quark decays exclusively to tH, the observed (expected) lower limit on the mass of the T quark is 745 (773) GeV/c2 at 95% confidence level. For the first time an algorithm is used for tagging boosted Higgs bosons that is based on a combination of jet substructure information and b tagging.
Book Synopsis Measurements of WH and ZH Production in the H->bb Decay Channel in Pp Collisions at 13TeV with the ATLAS Detector by : ATLAS Collaboration CERN
Download or read book Measurements of WH and ZH Production in the H->bb Decay Channel in Pp Collisions at 13TeV with the ATLAS Detector written by ATLAS Collaboration CERN and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Measurements of the Standard Model Higgs boson decaying into a bb ̄ pair and produced in association with a W or Z boson decaying into leptons, using proton-proton collision data collected between 2015 and 2018 by the ATLAS detector, are presented. The measurements use collisions produced by the Large Hadron Collider at a centre-of-mass energy of s√=13TeV, corresponding to an integrated luminosity of 139fb−1. The production of a Higgs boson in association with a W or Z boson is established with observed (expected) significances of 4.0 (4.1) and 5.3 (5.1) standard deviations, respectively. Cross-sections of associated production of a Higgs boson decaying into bottom quark pairs with an electroweak gauge boson, W or Z, decaying into leptons are measured as a function of the gauge boson transverse momentum in kinematic fiducial volumes. The cross-section measurements are all consistent with the Standard Model expectations, and the total uncertainties vary from 30% in the high gauge boson transverse momentum regions to 85% in the low regions. Limits are subsequently set on the parameters of an effective Lagrangian sensitive to modifications of the WH and ZH processes as well as the Higgs boson decay into bb ̄
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