A Search For Supersymmetric Top Quarks In Cms 8tev Data In The B Tau Jets Met Muon Final State
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A Search For Supersymmetric Top Quarks In Cms 8tev Data In The B Tau Jets Met Muon Final State
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Author : Andrew Malone Melo
language : en
Publisher:
Release Date : 2016
A Search For Supersymmetric Top Quarks In Cms 8tev Data In The B Tau Jets Met Muon Final State written by Andrew Malone Melo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Electronic dissertations categories.
Searches For Supersymmetric Particles In Final States With Multiple Top And Bottom Quarks With The Atlas Detector
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Author : Chiara Rizzi
language : en
Publisher: Springer Nature
Release Date : 2020-09-01
Searches For Supersymmetric Particles In Final States With Multiple Top And Bottom Quarks With The Atlas Detector written by Chiara Rizzi and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-09-01 with Science categories.
This PhD thesis documents two of the highest-profile searches for supersymmetry performed at the ATLAS experiment using up to 80/fb of proton-proton collision data at a center-of-mass energy of 13 TeV delivered by the Large Hadron Collider (LHC) during its Run 2 (2015-2018). The signals of interest feature a high multiplicity of jets originating from the hadronisation of b-quarks and large missing transverse momentum, which constitutes one of the most promising final state signatures for discovery of new phenomena at the LHC. The first search is focused on the strong production of a pair of gluinos, with each gluino decaying into a neutralino and a top-antitop-quark pair or a bottom-antibottom-quark pair. The second search targets the pair production of higgsinos, with each higgsino decaying into a gravitino and a Higgs boson, which in turn is required to decay into a bottom-antibottom-quark pair. Both searches employ state-of-the-art experimental techniques and analysis strategies at the LHC, resulting in some of the most restrictive bounds available to date on the masses of the gluino,neutralino, and higgsino in the context of the models explored.
Search For Supersymmetry In The Jets Met Taus Final State Using The Cms Detector At The Lhc
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Author : Roy Joaquin Montalvo
language : en
Publisher:
Release Date : 2013
Search For Supersymmetry In The Jets Met Taus Final State Using The Cms Detector At The Lhc written by Roy Joaquin Montalvo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
In this dissertation results are presented from a search for the pair production of heavy colored particles (gluinos, squarks) in R-parity conserving supersymmetric models, in which the lightest supersymmetric particle is a stable and neutral object. The search was performed for events with at least two tau leptons, two highly energetic jets and large missing transverse momentum in the final state on a data sample of proton-proton collisions at sqrt(s) = 7 TeV. The data sample was collected by the Compact Muon Solenoid detector at the Large Hadron Collider in 2011, and it corresponds to an integrated luminosity of 5fb -1. The tau isolation variable was optimized for this search. The number of events corresponding to standard model processes in the final selection was estimated to be 7.49 plus - minus 0.74 using background estimation techniques based on data. Nine observed events are found to be in agreement with the standard model prediction, and exclusion limits on gluino mass are obtained in the context of supersymmetric models at the 95% confidence level. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149247
Search For A Vector Like Quark T Decaying Into Top Higgs In Single Production Mode In Full Hadronic Final State Using Cms Data Collected At 8 Tev
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Author : José David Ruiz Alvarez
language : en
Publisher:
Release Date : 2015
Search For A Vector Like Quark T Decaying Into Top Higgs In Single Production Mode In Full Hadronic Final State Using Cms Data Collected At 8 Tev written by José David Ruiz Alvarez and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
During 2012, the Large Hadron Collider (LHC) has delivered proton-proton collisions at 8 TeV center of mass energy to the ATLAS and CMS experiments. These two experiments have been designed to discover the Higgs boson and to search for new particles predicted by several theoretical models, as supersymmetry. The Higgs boson has been discovered by ATLAS and CMS experiments on July, 4th of 2012, starting a new era of discoveries in particle physics domain. With the confirmation of the existence of the Higgs boson, searches for new physics involving this boson are of major interest. In particular, data can be used to look for new massive particles that decay into the Higgs boson accompanied with other particles of the standard model. One expected signature is a Higgs boson produced with a top quark, the two heaviest particles in the standard model. The standard model predicts a cross section of top-Higgs production, then any enhancement of their associated production will be a clear signature of physics beyond the standard model. In addition, the existence of physics beyond the standard model can also be reflected by resonances that decay into a top-quark and a Higgs boson. In the first part of my work I describe the theoretical and experimental foundations of the standard model, as well as the experimental device. In the same theoretical chapter, I also discuss the formulation of an extension of the standard model. In addition, I describe a feasibility study of a search of one of the particles predicted by such model. The second part contains the realization of the search for a top partner, T_, within the CMS experiment. This top partner is a new particle very similar to the standard model top quark, but much heavier, that can decay into a top quark and a Higgs boson. The analysis looks for this particle in the full hadronic final state, where the Higgs boson decays into two b-quarks and the top quark decays into three standard model quarks, a b and two light quarks. In this channel, I reconstruct its mass from the identification of all its decay products. As a result of the analysis, I show the limits on the T_ production cross section from the number of observed events in the specific signature.
Scalar Top Quark Search With Jets And Missing Momentum In Pp Collisions At 7 Tev
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Author : Mariarosaria D'Alfonso
language : en
Publisher:
Release Date : 2012
Scalar Top Quark Search With Jets And Missing Momentum In Pp Collisions At 7 Tev written by Mariarosaria D'Alfonso and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
The results of CMS searches for Supersymmetry are interpreted in the context of Simplified Models. A limited set of hypothetical particles and decay chains are introduced to produce a given topological signature. The amplitudes describing the production and decays of these particles are parametrized in terms of the particle massesand their branching ratios to daughter particles. Among the new possible particles, the Higgs mechanism of electroweak symmetry breaking gives a special role to the partnerof the third generation SM particles. In this thesis, I will describe how the comparison of different search strategies on multiple simplified models helps to quantify that the LHC has not put any stringent bounds on them yet. The 4.98 /fb of data collected by CMS, was analyzed to search for the scalar stop in the jets plus met final state. In particular, I will focus on the ttbar background; I will describe in detail the handles used to reduce it and the technique adopted to predict this contribution from data. The data is found to be in agreement with the predicted backgrounds. An upper limit on the cross section times branching ratio is set for the decays stop to LSP plus top and stop to LSP plus b W through a chargino final state.
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
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Author :
language : en
Publisher:
Release Date : 2016
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 has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
A search for single production of vector-like top quark partners (T) decaying into a Higgs boson and a top quark is performed using data from pp collisions at a centre-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The top quark decay includes an electron or a muon while the Higgs boson decays into a pair of b quarks. No significant excess over standard model backgrounds is observed. Exclusion limits on the product of the production cross section and the branching fraction are derived in the T quark mass range 700 to 1800 GeV. For a mass of 1000 GeV, values of the product of the production cross section and the branching fraction greater than 0.8 and 0.7 pb are excluded at 95% confidence level, assuming left- and right-handed coupling of the T quark to standard model particles, respectively. This is the first analysis setting exclusion limits on the cross section of singly produced vector-like T quarks at a centre-of-mass energy of 13 TeV.
Search For Direct Pair Production Of Scalar Top Quarks In The Single And Dilepton Channels In Proton Proton Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2016
Search For Direct Pair Production Of Scalar Top Quarks In The Single And Dilepton Channels In Proton Proton Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Results are reported from a search for the top squark $ \tilde{t}_1 $, the lighter of the two supersymmetric partners of the top quark. The data sample corresponds to 19.7 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} =$ 8 TeV collected with the CMS detector at the LHC. The search targets $ \tilde{t}_1 \to \mathrm{b} \tilde{\chi}^{\pm}_1$ and $ \tilde{t}_1 \to \mathrm{t}^{(*)} \tilde{\chi}^0_1$ decay modes, where $\tilde{\chi}^{\pm}_1$ and $\tilde{\chi}^0_1$ are the lightest chargino and neutralino, respectively. The reconstructed final state consists of jets, b jets, missing transverse energy, and either one or two leptons. Leading backgrounds are determined from data. No significant excess in data is observed above the expectation from standard model processes. The results exclude a region of the two-dimensional plane of possible $ \tilde{t}_1 $ and $\tilde{\chi}^0_1 $ masses. The highest excluded $ \tilde{t}_1 $ and $ \tilde{\chi}^0_1$ masses are about 700 GeV and 250 GeV, respectively.
Search For Pair Production Of Scalar Top Quarks Decaying To A Tau Lepton And A B Quark In Ppbar Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2008
Search For Pair Production Of Scalar Top Quarks Decaying To A Tau Lepton And A B Quark In Ppbar Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
We present the results of a search for pair production of scalar top quarks ({tilde t}1) in an R-parity violating supersymmetric scenario using 322 pb−1 of p{bar p} collisions at √s = 1.96 TeV collected by the upgraded Collider Detector at Fermilab. We assume each {tilde t}1 decays into a? lepton and a b quark with a branching ratio?, and that the final state contains either an electron or a muon from a leptonic? decay, a hadronically decaying? lepton, and two or more jets. Two candidate events pass our final selection criteria, consistent with the expectation from standard model processes. We present upper limits on the cross section times branching ratio squared?({tilde t}1{bar {tilde t}}1) x?2 as a function of the stop mass m({tilde t}1). Assuming? = 1, we set a 95% confidence level limit m({tilde t}1)> 153 GeV=c2 obtained using a next-to-leading order cross section. These limits are also fully applicable to the case of a pair produced third generation scalar leptoquark decaying into a? lepton and a b quark.
Search For Direct Pair Production Of Supersymmetric Top Quarks Decaying To All Hadronic Final States In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2016
Search For Direct Pair Production Of Supersymmetric Top Quarks Decaying To All Hadronic Final States In Pp Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Here, results are reported from a search for the pair production of top squarks, the supersymmetric partners of top quarks, in final states with jets and missing transverse momentum. The data sample used in this search was collected by the CMS detector and corresponds to an integrated luminosity of 18.9 fb–1 of proton-proton collisions at a centre-of-mass energy of 8 TeV produced by the LHC. The search features novel background suppression and prediction methods, including a dedicated top quark pair reconstruction algorithm. The data are found to be in agreement with the predicted backgrounds. Exclusion limits are set in simplified supersymmetry models with the top squark decaying to jets and an undetected neutralino, either via a top quark or through a bottom quark and chargino. Models with the top squark decaying via a top quark are excluded for top squark masses up to 755 GeV in the case of neutralino masses below 200 GeV. For decays via a chargino, top squark masses up to 620 GeV are excluded, depending on the masses of the chargino and neutralino.
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
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Author : ATLAS Collaboration CERN
language : en
Publisher:
Release Date : 2021
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 has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
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