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| Author | : Kilian Rosbach |
| Publisher | : |
| Total Pages | : 181 |
| Release | : 2015 |
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| Author | : Johanna Gramling |
| Publisher | : Springer |
| Total Pages | : 290 |
| Release | : 2018-08-01 |
| Genre | : Science |
| ISBN | : 3319950169 |
This book discusses searches for Dark Matter at the CERN’s LHC, the world’s most powerful accelerator. It introduces the relevant theoretical framework and includes an in-depth discussion of the Effective Field Theory approach to Dark Matter production and its validity, as well as an overview of the formalism of Simplified Dark Matter models. Despite overwhelming astrophysical evidence for Dark Matter and numerous experimental efforts to detect it, the nature of Dark Matter still remains a mystery and has become one of the hottest research topics in fundamental physics. Two searches for Dark Matter are presented, performed on data collected with the ATLAS experiment. They analyze missing-energy final states with a jet or with top quarks. The analyses are explained in detail, and the outcomes and their interpretations are discussed, also in view of the precedent analysis of theoretical approaches. Given its depth of coverage, the book represents an excellent reference guide for all physicists interested in understanding the theoretical and experimental considerations relevant to Dark Matter searches at the LHC.
| Author | : ATLAS Collaboration CERN |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2021 |
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| ISBN | : |
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
| Author | : Maria Elena Stramaglia |
| Publisher | : |
| Total Pages | : |
| Release | : 2016 |
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| Author | : Matthew Anthony |
| Publisher | : |
| Total Pages | : |
| Release | : 2020 |
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| Author | : Xiaoxiao Wang |
| Publisher | : |
| Total Pages | : 486 |
| Release | : 2015 |
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| Author | : |
| Publisher | : |
| Total Pages | : 206 |
| Release | : 2002 |
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Supersymmetric partners of top quarks, stops, will be pair produced at the Fermi National Accelerator Laboratory in proton-antiproton collisions at a center-of-mass energy √s= 1.8TeV if kinematically accessible. Within the framework of the Minimal Supersymmetric extension of the Standard Model, the stop quarks are assumed to decay into a lepton, a bottom quark and a supersymmetric neutrino, sneutrino. Thus the experimental signature of stop presence in the data would be two opposite electric charge leptons, hadronic jets and substantial energy imbalance in the detector due to the escaping, undetected sneutrinos. We searched a total of ∫ Ldt = 107.2 pb-1 of data collected by the Collider Detector at Fermilab experiment. No evidence of a stop signal has been found which allows us to calculate a 95% con dence level upper limit on the number of stop-originated events in the data of this size. We have translated this into a 95% con dence level exclusion region in the stop versus sneutrino mass plane.
| Author | : |
| Publisher | : |
| Total Pages | : 160 |
| Release | : 2010 |
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We report the result of a search for the pair production of the lightest supersymmetric partner of the top quark ({tilde t}1) in 5.4 ± 0.3 fb−1 of data from the D0 detector at a p{bar p} center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The scalar top quarks are assumed to decay into a b quark, a charged lepton and a scalar neutrino ({tilde {nu}}), and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected and new exclusion limits at the 95% C.L. are set for a portion of the (m{sub {tilde t}1}, m{sub {tilde {nu}}}) mass plane.
| Author | : Avik Roy (Ph. D.) |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2021 |
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This thesis presents the search for a heavy, up-type vector-like quark (VLQ), or Top Partner, with charge +2/3. Top Partners are predicted in well motivated models of new physics beyond the Standard Model. Having collected data with the ATLAS detector during 2015-2018 run of the LHC at a center-of-mass energy of 13 TeV, I describe in this dissertation an analysis searching for Top Partners produced by the fusion of a W boson and a bottom quark and decaying into a Z boson and a top quark with a kinematic signature of three leptons. Since the search performed by analyzing the data collected in 2015-16 does not provide sufficient evidence in favor of VLQ discovery, we set limits on Top Partner mass as a function of its coupling constants. In order to extend this search for the entire dataset collected by ATLAS in Run 2 and facilitate a general interpretation and combination of all single VLQ searches in ATLAS, a generalized, semi-analytical framework for model-independent interpretation of the results of a generic search for the single production of VLQs in terms of the free parameters in the VLQ Lagrangian is presented. Additional studies are performed to facilitate computationally manageable signal generation for a fine grid of VLQ mass and couplings, probe interference between VLQ and standard model processes, and quantify contribution of sub-dominant diagrams. Finally, an updated analysis strategy to expand the previously mentioned search for the entire Run 2 dataset is described with initial results for kinematic distributions as well as expected limits on cross-sections, Top Partner masses, and couplings
| Author | : Rafał Bielski |
| Publisher | : |
| Total Pages | : |
| Release | : 2018 |
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| ISBN | : |
