Search For New Phenomena With Top Quark Pairs In Final States With One Lepton Jets And Missing Transverse Momentum In Pp Collisions At Square Roots PDF Download
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| Author | : ATLAS Collaboration CERN |
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| Total Pages | : 0 |
| Release | : 2021 |
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Download 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 Book in PDF, ePub and Kindle
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
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| Release | : 2015 |
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Download Search for New Phenomena in Final States with an Energetic Jet and Large Missing Transverse Momentum in Pp Collisions at \(\sqrt{s{\mathrm{}}} Book in PDF, ePub and Kindle
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb-1 of \(\sqrt{s{\mathrm{}}} = 8\) TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT>120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between EmissT>150 GeV and EmissT>700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. Limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presented.
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| Release | : 2015 |
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Download Observation of Top-quark Pair Production in Association with a Photon and Measurement of the Tt{u00AF}? Production Cross Section in pp Collisions at {u221A}s Book in PDF, ePub and Kindle
A search is performed for top-quark pairs (tt¯) produced together with a photon (?) with transverse energy greater than 20 GeV using a sample of tt¯ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of 4.59 fb−1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 tt¯? candidate events are observed in the electron and muon channels, to be compared to the expectation of 79 ± 26 and 120 ± 39 non-tt¯? background events, respectively. The production of tt¯? events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The tt¯? production cross section times the branching ratio (BR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is ?fidtt¯? × BR = 63 ± 8(stat)+17–13(syst) ± 1(lumi) fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48 ± 10 fb.
| Author | : [Study Group] ATLAS Collaboration CERN |
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| Total Pages | : 0 |
| Release | : 2022 |
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Download Search for New Phenomena in Three- Or Four-lepton Events in Pp Collisions at [square Root]s Book in PDF, ePub and Kindle
Abstract: A search with minimal model dependence for physics beyond the Standard Model in events featuring three or four charged leptons (3l and 4l, ) is presented. The analysis aims to be sensitive to a wide range of potential new-physics theories simultaneously. This analysis uses data from pp collisions delivered by the Large Hadron Collider at a centre-of-mass energy of TeV and recorded with the ATLAS detector, corresponding to the full Run 2 dataset of 139 fb−1. The 3l and 4l phase space is divided into 22 event categories according to the number of leptons in the event, the missing transverse momentum, the invariant mass of the leptons, and the presence of leptons originating from a Z-boson candidate. These event categories are analysed independently for the presence of deviations from the Standard Model. No statistically significant deviations from the Standard Model predictions are observed. Upper limits for all signal regions are reported in terms of the visible cross-section
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| Release | : 2016 |
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Download Search for New Phenomena in Final States with an Energetic Jet and Large Missing Transverse Momentum in Pp Collisions at S Book in PDF, ePub and Kindle
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 3.2 fb–1 at √s=13 TeV collected in 2015 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons. Several signal regions are considered with increasing missing-transverse-momentum requirements between EmissT > 250 GeV and EmissT > 700 GeV. Good agreement is observed between the number of events in data and Standard Model predictions. Here, the results are translated into exclusion limits in models with large extra spatial dimensions, pair production of weakly interacting dark-matter candidates, and the production of supersymmetric particles in several compressed scenarios.
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| Release | : 2014 |
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Download Search for New Phenomena in Tt Events with Large Missing Transverse Momentum Book in PDF, ePub and Kindle
The ATLAS Run I data as provided by CERN's LHC has been systematically searched for the presence of supersymmetric partners of the top quark (stops) using the identification of charm-flavored jets and boosted top tagging. No signs of stop could be established yet.
| Author | : ATLAS Collaboration CERN |
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| Total Pages | : 0 |
| Release | : 2018 |
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Download Search for Squarks and Gluinos in Final States with Jets and Missing Transverse Momentum Using 36 Fb[minus]1 of [square Root]s Book in PDF, ePub and Kindle
Abstract: A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded in 2015 and 2016 by the ATLAS experiment in √s=13 TeV proton-proton collisions at the Large Hadron Collider, corresponding to an integrated luminosity of 36.1 fb−1. The results are interpreted in the context of various models where squarks and gluinos are pair produced and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.03 TeV for a simplified model incorporating only a gluino and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.55 TeV are excluded if the lightest neutralino is massless. These limits substantially extend the region of supersymmetric parameter space previously excluded by searches with the ATLAS detector
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| Total Pages | : 39 |
| Release | : 2014 |
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Download A Search for Flavour Changing Neutral Currents in Top-quark Decays in Pp Collision Data Collected with the ATLAS Detector at √s Book in PDF, ePub and Kindle
A search for flavour changing neutral current (FCNC) processes in top-quark decays by the ATLAS Collaboration is presented. Data collected from pp collisions at the LHC at a centre-of-mass energy of √s = 7 TeV during 2011, corresponding to an integrated luminosity of 2.1 fb−1, were used. A search was performed for top-quark pair-production events, with one top quark decaying through the t → Zq FCNC (q = u, c) channel, and the other through the Standard Model dominant mode t → Wb. Only the decays of the Z boson to charged leptons and leptonic W-boson decays were considered as signal. Consequently, the final-state topology is characterised by the presence of three isolated charged leptons, at least two jets and missing transverse momentum from the undetected neutrino. No evidence for an FCNC signal was found. An upper limit on the t → Zq branching ratio of BR(t → Zq)
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| Total Pages | : 39 |
| Release | : 2012 |
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Download A Search for Flavour Changing Neutral Currents in Top-quark Decays in Pp Collision Data Collected with the ATLAS Detector at {u221A}s Book in PDF, ePub and Kindle
A search for flavour changing neutral current (FCNC) processes in top-quark decays by the ATLAS Collaboration is presented. Data collected from pp collisions at the LHC at a centre-of-mass energy of √s = 7 TeV during 2011, corresponding to an integrated luminosity of 2.1 fb−1, were used. A search was performed for top-quark pair-production events, with one top quark decaying through the t → Zq FCNC (q = u, c) channel, and the other through the Standard Model dominant mode t → Wb. Only the decays of the Z boson to charged leptons and leptonic W-boson decays were considered as signal. Consequently, the final-state topology is characterised by the presence of three isolated charged leptons, at least two jets and missing transverse momentum from the undetected neutrino. No evidence for an FCNC signal was found. An upper limit on the t → Zq branching ratio of BR(t → Zq)
| Author | : Charles Vincent Welke |
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| Total Pages | : 142 |
| Release | : 2016 |
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Download A Search for New Physics in Final States With Two Opposite-SignSame-Flavor Leptons, Jets, and Missing Transverse Energy InProton-Proton Collisions with a Center of Mass Energy of 13 TeV Book in PDF, ePub and Kindle
A search is performed in final states with Z$\rightarrow\ell\ell$, jets, and missing transverse momentum using data collected with the CMS detector at the CERN LHC in 2015 corresponding to an integrated luminosity of 2.3~\fbinv of pp collisions at $\sqrt{s}=13$\TeV. Signal regions are defined to maximize sensitivity to new physics including one to search where ATLAS reported a 3.0~$\sigma$ excess at 8~TeV. The observations in all regions are consistent with the predicted standard model backgrounds, and the results are interpreted in the context of simplified models of supersymmetry.
