Download or read book Search for Top antitop Quark Resonances in the Lepton jets Final State with the CMS Detector Preparing the Run 3 Analysis written by Johanna Matthiesen and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for mathrm T bar t Resonances in Highly boosted Lepton jets and Fully Hadronic Final States in Proton proton 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: A search for the production of heavy resonances decaying into top quark-antiquark pairs is presented. The analysis is performed in the lepton+jets and fully hadronic channels using data collected in proton-proton collisions at $\sqrt{s}$ =13 TeV using the CMS detector at the LHC, corresponding to an integrated luminosity of 2.6 inverse femtobarns. The selection is optimized for massive resonances, where the top quarks have large Lorentz boosts. No evidence for resonant ttbar production is found in the data, and upper limits on the production cross section of heavy resonances are set. The exclusion limits for resonances with masses above 2 TeV are significantly improved compared to those of previous analyses at $\sqrt{s}$ = 8 TeV.
Download or read book Search for Heavy Resonance Decays Into Top quark Pairs Using a Lepton plus jets Final State in Proton proton Collisions at s written by Kyle Krowpman and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents two studies in a search for new heavy resonances with 139 fb-1 of proton-proton collisions delivered by the Large Hadron Collider at √s = 13 TeV as measured by the ATLAS detector. In many Standard Model extensions, the top quark plays an important role in the dynamics of electroweak symmetry breaking, and so the studies presented here focus on heavy resonance searches in the top-antitop decay channel and their combination with searches for heavy resonances decaying into other final states. The first study detailed in this thesis is a search for new heavy resonances in a semileptonically decaying top-antitop final state where no significant excesses of data were observed with respect to the background prediction. That being so, exclusion limits at the 95% confidence level were placed on possible resonant masses for a Z′ in a leptophobic topcolor-assisted technicolor model and for a bulk Randall-Sundrum graviton at 4.2 TeV and 1.0 TeV, respectively. This top-antitop search was combined with searches in orthogonal final states performed by the ATLAS Collaboration from which limit contours were placed at the 95% confidence level in the space of couplings to Standard Model particles for the Heavy Vector Triplet model.
Download or read book Search for Top antitop Quark Resonances with the ATLAS Detector at the Large Hadron Collider written by Bertrand Chapleau and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The intriguing nature of the top quark, by far the heaviest particle in the Standard Model of particle physics, has motivated the development of many theoretical extensions predicting the existence of new massive particles decaying to a pair of top-antitop quarks. The production of these hypothetical particles in proton-proton collisions at the Large Hadron Collider would reveal itself as a resonance in the expected smooth distribution of the top-antitop quark invariant mass. This thesis presents a search for such a new heavy particle decaying to a pair of top-antitop quarks in the semi-leptonic final state. The analyzed data sample amounts to a total of 4.6 fb-1 at a proton-proton collision center-of-mass energy of 7 TeV. Novel techniques specifically tailored to the identification of the decay products of highly energetic top quarks are developed and used. No evidence for resonant production of pairs of top-antitop quarks is found and, as a result, constraints are set on two theoretical models. Upper limits on the production cross-section times branching ratio are established at a 95% credibility level for a leptophobic Zʹ boson from the Topcolor model, and a Kaluza-Klein gluon from the Randall-Sundrum model. The Zʹ boson and the Kaluza-Klein gluon are excluded to exist (at a 95% credibility level) in the mass ranges 0.8-1.65 TeV and 0.8-1.88 TeV, respectively. The constraints de- rived in this thesis on the two theoretical models are more stringent than the ones obtained at other experiments, thanks to the large center-of-mass energy and the dedicated high-energy top quark identification techniques used." --
Download or read book A Search for Massive Resonances in Final States with Boosted Top antitop Pairs Decaying Into a Lepton and Jets with the ATLAS Detector at the Large Hadron Collider written by Janna Katharina Behr and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Search for Tt Resonances in the Single Lepton Final State with the ATLAS Experiment written by Andrew David Altheimer and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for undiscovered particles decaying into top-antitop quark pairs produced in proton-proton collisions with the ATLAS experiment at the Large Hadron Collider utilizing 20.3 fb$^-1$ of data collected at $\sqrt{s}=8$ \tev\ center-of-mass energy during the 2012 data taking period is presented. The invariant mass spectrum of events containing multiple jets, exactly one lepton, and missing transverse energy and which are consistent with the decay of a top-antitop quark pair is studied and found to be consistent with that predicted by the Standard Model. Upper limits on the production cross section times branching ratio of several benchmark signal models are set at a 95\% confidence level.
Download or read book Search for a Heavy Resonance Decaying to a Top Quark and a Vector like Top Quark 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: A search is presented for massive spin-1 Z' resonances decaying to a top quark and a heavy vector-like top quark partner T. The search is based on a 2.6 inverse femtobarns sample of proton-proton collisions at 13 TeV collected with the CMS detector at the LHC. The analysis is optimized for final states in which the T quark decays to a W boson and a bottom quark. The focus is on all-jet final states in which both the W boson and the top quark decay into quarks that evolve into jets. The decay products of the top quark and of the W boson are assumed to be highly Lorentz-boosted and cannot be reconstructed as separate jets, but are instead reconstructed as merged, wide jets. Techniques for the identification of jet substructure and jet flavour are used to distinguish signal from background events. Several models for Z' bosons decaying to T quarks are excluded at 95% confidence level, with upper limits on the cross section ranging from 0.13 to 10 pb, depending on the chosen hypotheses. This is the first search for a neutral spin-1 heavy resonance decaying to a top quark and a vector-like T quark in the all-hadronic final state.
Download or read book Analytic Mass Reconstruction of Top antitop Resonances in the Dilepton Channel at ATLAS written by Michelle Renée Boudreau and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many theories beyond the Standard Model predict new massive particles that decay preferentially to top-antitop quark pairs. This thesis investigates the dilepton final state where both W bosons from the top quarks decay into leptons. This final state features the highest purity for top quarks but is kinematically under-constrained due to the presence of the two neutrinos that leave the ATLAS detector undetected. Using kinematic constraints from the top-antitop quark decay chain, along with the missing energy, leptons, and jets, that are measured with the ATLAS detector, a set of analytic solutions for the four-vectors of the neutrinos can be obtained. With this information, the invariant mass can be reconstructed up to a four-fold ambiguity. Methods used to eliminate incorrect neutrino solutions are investigated and characterized. For a resonance particle with a mass much larger than the top quark mass, the top quarks will be highly boosted, resulting in collimated decay products of the top quark. Optimizing the lepton selection in such an environment is very important and is also discussed.
Download or read book Searches for Light and Heavy flavor Three jet Resonances in Proton proton Collisions with the CMS Detector at sqrt s written by and published by . This book was released on 2014 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for three-jet hadronic resonance production in proton-proton collisions at 8 TeV center-of-mass energy has been conducted by the CMS Collaboration at the LHC. The data set corresponds to an integrated luminosity of 19.4 fb-1. The search method is modelindependent. Events are selected that contain a large number of jets with high transverse momentum. An ensemble of jets is used to extract a new possible signal from copious QCD background. Event selection is optimized using a benchmark model where supersymmetric gluinos are pair-produced and each of the gluinos decays exclusively into three jets. Two scenarios of this decay are considered denoted by the RPV couplings [lambda]'' 112 and [lambda]'' 113 or [lambda]'' 223. The first coupling allows for gluinos to decay into only light-flavor jets, while the latter two allow decays into one heavy-flavor and two light-flavor jets. No significant deviation is found between the selected events and the expected standard model multijet and t$\bar{t}$ background. For gluinos decaying through 00 112, masses below 650 GeV are excluded at the 95% confidence level. The search including heavy-flavor jets in the final state with the couplings [lambda]'' 113 or [lambda]'' 223 is the first of its kind. Gluinos decaying into one heavy-flavor and two light-flavor jets are excluded for masses between 200 and 835 GeV.
Download or read book Search for Resonant t bar t Production in Proton proton Collisions at u221A s written by and published by . This book was released on 2016 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is performed for the production of heavy resonances decaying into top-antitop quark pairs in proton-proton collisions at √s = 8 TeV. Data used for the analyses were collected with the CMS detector and correspond to an integrated luminosity of 19.7 fb–1. The search is performed using events with three different final states, defined by the number of leptons (electrons and muons) from the tt¯ → WbWb decay. The analyses are optimized for reconstruction of top quarks with high Lorentz boosts, where jet substructure techniques are used to enhance the sensitivity. Results are presented for all channels and a combination is performed. Furthermore, no significant excess of events relative to the expected yield from standard model processes is observed.
Download or read book Search for Massive Top Resonances Using Jet Substructure at CMS written by James W. Dolen and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is presented for a new massive particle, generically referred to as a Z', decaying into a top anti-top quark pair, which then decay hadronically. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis uses data collected by the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) at CERN in 2011. The dataset contains 4.92 fb−1 of integrated luminosity from proton-proton collisions at a center of mass energy of 7 TeV. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall-Sundrum Kaluza-Klein gluon. In addition, any enhancement to t t-bar production for invariant masses above 1 TeV/c2 in the standard model is constrained.
Download or read book Search for Resonant Production of Top Antitop Pairs Decaying Into Multi jets at the Collider Detector at Fermilab written by Yuri Oksuzian and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: We performed a search for"non-standard model tṫ resonances in the all jets final state channel." The main goal was to examine top-antitop invariant mass spectrum for the presence of narrow resonant states. The data analysis used 2.8fb−1 of CDF data; events were produced at the Tevatron collider in p[bar p] collisions with center-of-mass energy of 1.96 TeV. 2086 data events were analyzed and compared to Standard Model expectation. No evidence for new tṫ resonant production mechanisms was found. Upper limits were placed on the cross-section times branching ratio for resonance production at 805 GeV/c2. For signal modeling we considered leptophobic Z' boson in a topcolor-assisted technicolor model with the width of [capital gamma]= 1.2%MX0.
Download or read book A Search for t overline t Resonances Using Lepton plus jets Events in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for new particles that decay into top quark pairs is reported. The search is performed with the ATLAS experiment at the LHC using an integrated luminosity of 20.3 fb-1 of proton-proton collision data collected at a centre-of-mass energy of \(\sqrt{s}=8 \) TeV. The lepton-plus-jets final state is used, where the top pair decays to \({W}^{+}b{W}^{-}\overline{b} \), with one W boson decaying leptonically and the other hadronically. The invariant mass spectrum of top quark pairs is examined for local excesses or deficits that are inconsistent with the Standard Model predictions. No evidence for a top quark pair resonance is found, and 95% confidence-level limits on the production rate are determined for massive states in benchmark models. The upper limits on the cross-section times branching ratio of a narrow Z' boson decaying to top pairs range from 4.2 pb to 0.03 pb for resonance masses from 0.4 TeV to 3.0 TeV. A narrow leptophobic topcolour Z' boson with mass below 1.8 TeV is excluded. Upper limits are set on the cross-section times branching ratio for a broad colour-octet resonance with [Gamma]/m = 15% decaying to \(t\overline{t} \). These range from 4.8 pb to 0.03 pb for masses from 0.4 TeV to 3.0 TeV. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.2 TeV.
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 $
Download or read book Cross Section Measurement and Search for New Physics with Top Quark Pair Events Involving a Tau Lepton in ATLAS written by Jennifer Lynn Godfrey and published by . This book was released on 2013 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2011, the ATLAS detector recorded an integrated luminosity of over 5 fb−1 of proton-proton collisions delivered by the LHC at a centre-of-mass square root of s = 7 TeV. The first of two analyses is a test of the standard model and the world's most precise measurement of the top quark pair production cross section for final states which include a hadronically decaying tau lepton. The second analysis uses the same dataset to search for a charged Higgs boson, also resulting in the world's best limits for the search channel. In the cross section measurement, 2.1 fb−1 of ATLAS proton-proton collision data is used to measure the top quark pair production cross section in events containing an isolated electron or muon and a tau lepton decaying hadronically. After initial event requirements, the leading background comes from top quark pairs with jets faking tau leptons. A fit to a tau lepton identification variable is used to determine the signal yield. The measured cross section, [sigma][subscript{tt̄}] 186±13(stat.)±2019(syst.)±7(lumi.)pb, is in good agreement with the standard model prediction. Several extensions to the standard model predict the existence of at least one charged Higgs boson, H[superscript ±]. According to these extensions, the top quark can decay into a bottom quark and a light charged Higgs boson in addition to the standard model decay to a bottom quark and aW boson. In the second analysis, event yield ratios between different final states are measured using 4.6 fb−1 of ATLAS data. This is compared to simulation to search for a violation of lepton universality. This ratio-based method reduces the impact of systematic uncertainties in the analysis. No significant deviations from the standard model predictions are observed. With the assumption that the charged Higgs boson branching ratio to a tau lepton and a neutrino is 100%, upper limits in the range 3.2%-4.4% can be placed on the top quark to charged Higgs branching ratio for 90 less than or equal to m[subscript {H[superscript ±]}] less than or equal to 140 GeV. After combination with results from a search for charged Higgs bosons in tt̄ decays using the thad+jets final state, upper limits on this branching ratio can be set in the range 0.8%-3.4%, for 90 less than or equal to m[subscript {H[superscript ±]}] less than or equal to 140 GeV.
Download or read book A Search for Top antitop Quark Resonances with the ATLAS Detector at the LHC written by Anna Duncan and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for Vector like Quark Production in the Lepton jets and Dilepton jets Final States Using 5 4 Fb 1 of Run II Data written by Seth Caughron and published by . This book was released on 2011 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
