Download or read book Searches for New Resonances Decaying to Top antitop Quark Pairs with the ATLAS Detector in Sqrt s written by Stephen Swedish and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 Resonances Decaying Into Top Quark Pairs Using Fully Hadronic Decays in Pp Collisions with ATLAS at Sqrt s written by Gregor Kasieczka and published by . This book was released on 2013 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for Heavy Resonances Decaying to Top Quark Pairs in the Boosted All Hadronic Decay Channel written by Trisha Farooque 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 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 A Search for Massive Resonances Decaying to Top Quark Pairs and Jet Trigger Performance Studies with the ATLAS Detector at the Large Hadron Collider written by and published by . This book was released on 2014 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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
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 194 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 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 Search for a New Resonance Decaying Into Top antitop at Tevatron written by Christian Schwanenberger and published by . This book was released on 2006 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this report a new search for a narrow-width heavy resonance decaying into top quark pairs (X {yields} t{bar t}) in p{bar p} collisions at {radical}s = 1.96 TeV has been performed using data collected by the D0 detector at the Fermilab Tevatron collider. The analysis considers t{bar t} candidate events in the lepton+jets channel using a lifetime tag to identify b-jets and the t{bar t} invariant mass distribution to search for evidence of resonant production. The analyzed dataset corresponds to an integrated luminosity of approximately 370 pb{sup -1}. Since no evidence for a t{bar t} resonance X is found, upper limits on {sigma}{sub x} x B(X {yields} t{bar t}) for different hypothesized resonance masses using a Bayesian approach are set. Within a topcolor-assisted technicolor model, the existence of a leptophobic Z' boson with M{sub Z'}
Download or read book Search for Resonances Decaying Into Top Quark Pairs Using Fully Hadronic Decays in Pp Collisions with ATLAS at s 327 7 TeV written by Gregor Kasieczka and published by . This book was released on 2013 with total page 155 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 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 Identification of Bottom quarks in Searches for New Heavy Resonances Decaying Into Boosted Top quarks with the ATLAS Detector and a Development of an Improved B tagging Algorithm written by Dominik Duda and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
