Searches For Supersymmetric Partners Of Third Generation Quarks And Measurement Of The Tt Z Process Using The Atlas Detector At The Cern Large Hadron Collider
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Third Generation Susy And T T Z Production
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Author : Josh McFayden
language : en
Publisher: Springer
Release Date : 2014-06-06
Third Generation Susy And T T Z Production written by Josh McFayden and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-06-06 with Science categories.
This thesis describes searches for new particles predicted by the super symmetry (SUSY) theory, a theory extending beyond the current Standard Model of particle physics, using the ATLAS detector at the CERN Large Hadron Collider. The thesis focuses on searches for stop and sbottom squarks, the SUSY partners of the top and bottom quarks, which are expected to be lighter than the partners of the first and second generation quarks and therefore good candidates for the first evidence of SUSY. It describes novel techniques for estimating and rejecting the Standard-Model backgrounds to searches for these particles. It also includes an independent analysis seeking to constrain the Standard Model ttZ background process, which also represents the first ATLAS search for this rare process at the LHC. The stop squark analysis described, with substantial leading contributions from the author, is the first search for these particles at the LHC to use the jets plus missing transverse energy plus 0-lepton signature and provides the world's best limits on the stop mass for light neutralino LSPs. All in all, the thesis describes three different world-leading analyses in both Standard Model and SUSY physics and therefore represents a major contribution to the field.
Searches For Supersymmetric Partners Of Third Generation Quarks And Measurement Of The Tt Z Process Using The Atlas Detector At The Cern Large Hadron Collider
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Author : Joshua McFayden
language : en
Publisher:
Release Date : 2014
Searches For Supersymmetric Partners Of Third Generation Quarks And Measurement Of The Tt Z Process Using The Atlas Detector At The Cern Large Hadron Collider written by Joshua McFayden and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Searches For Supersymmetric Partners Of Third Generation Quarks And Measurement Of The Tt Z Process Using The Atlas Detector At The Cern Large Hadron Collider
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Author : Joshua A. McFayden
language : en
Publisher:
Release Date : 2013
Searches For Supersymmetric Partners Of Third Generation Quarks And Measurement Of The Tt Z Process Using The Atlas Detector At The Cern Large Hadron Collider written by Joshua A. McFayden 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.
Third Generation Susy And T T Z Production
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Author : Josh McFayden
language : en
Publisher:
Release Date : 2014-06-30
Third Generation Susy And T T Z Production written by Josh McFayden and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-06-30 with categories.
Search For The Supersymmetric Partner Of The Top Quark With The Atlas Detector Via Tildet 1 Rightarrow T Widetilde Chi 0 1 And Tildet 1 Rightarrow B Widetilde Chi Pm 1 Decays
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Author : Francesca Consiglia Ungaro
language : en
Publisher:
Release Date : 2015
Search For The Supersymmetric Partner Of The Top Quark With The Atlas Detector Via Tildet 1 Rightarrow T Widetilde Chi 0 1 And Tildet 1 Rightarrow B Widetilde Chi Pm 1 Decays written by Francesca Consiglia Ungaro 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.
Zusammenfassung: The elementary particles composing matter and their interactions are described by the Standard Model of particle physics. The Standard Model of particle physics enabled predictions that were experimentally verified and has been confirmed throughout the past decades by data. Nevertheless, there are several theoretical reasons not to consider it as the ultimate theory.The strongest motivation to expect Physics beyond the Standard Model is the hierarchy problem. The radiative corrections to the mass of the Higgs boson grow quadratically with the square of the energy scale at which the Standard Model is considered to be valid. As a result, the parameters of the Standard Model need to be fine-tuned in order for the mass of the Higgs boson to acquire the value experimentally measured, despite the possibly large corrections.Supersymmetry is a promising theory extending the Standard Model which solves many of its shortcomings, including the hierarchy problem. Supersymmetry postulates a new fermion-boson symmetry resulting in the introduction of new particles, called superpartners, with the same quantum numbers and masses as the Standard Model particles, except for the spin, differing by half a unit. This new symmetry enables a cancellation of the radiative corrections due to the Standard Model particles with the corrections due to the newly introduced superpartners, contributing with opposite sign. Since no superpartners with the same mass as the Standard Model particles have been observed, Supersymmetry must be broken to allow the superpartners to have a mass different from the mass of the corresponding Standard Model particles.In the minimal version of Supersymmetry in terms of new particles, the Minimal Supersymmetric Standard Model, the hierarchy problem can still be solved with a moderate amount of fine-tuning if the masses of at least some of the superpartners are at the TeV energy scale. The conservation of a new multiplicative quantum number, the R-parity, can be assumed to prevent phenomena in contrast with experimental evidences, as the proton decay. Superpartners have R-parity -1, and Standard Model particles R-parity +1. If the conservation of R-parity is assumed, in collider experiments supersymmetric particles can only be produced in even numbers (usually two), and the lightest supersymmetric particles (LSP, usually taken to be the neutralino), is stable.The LHC (Large Hadron Collider), is a hadron collider able to accelerate protons to unprecedented energies. Between 2010 and 2012 it operated at a centre-of-mass energy of the proton-proton collisions of 7 and 8 TeV.Its general-purpose experiments, ATLAS (A Toroidal LHC Apparatus) and CMS (Compact Muon Spectrometer) collected data corresponding to about 5 $fb^{-1}$ at $\sqrt{s}$ = 7 TeV and 20 $fb^{-1}$ at $\sqrt{s}$ = 8 TeV. The LHC and its experiments have been built with the main motivations of searching for the Higgs boson, discovered by the ATLAS and CMS experiments in 2012, and searching for signals of Supersymmetry.There are strong theoretical reasons to expect the supersymmetric particles to lie at the TeV energy scale, which would make them accessible at the LHC.In the Minimal Supersymmetric Standard Model, the lightest superpartner of the top quark, light stop is very likely to be lighter than the superpartners of the other quarks. This thesis focuses on the search for direct stop pair production with the data collected by the ATLAS experiment. Two analyses have been performed, addressing different final states and decay modes.The first analysis targets stop masses close to the mass of the top quark, ideal to solve the hierarchy problem.The mass spectrum assumed is such that m(stop)
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
Search For Fourth Generation Quarks In The Dilepton Channel At Atlas With Sqrt S
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Author : Michael Werth
language : en
Publisher:
Release Date : 2012
Search For Fourth Generation Quarks In The Dilepton Channel At Atlas With Sqrt S written by Michael Werth 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.
A search is presented for heavy-quark pair production (QQ̄) under the decay hypothesis QQ̄ to W+qW-q̄ with q = u,d,c,s,b. The search is performed with 1.04 fb-1 of integrated luminosity from pp collisions at √s = 7 TeV collected by the ATLAS detector at the CERN Large Hadron Collider (LHC). Events are selected with two oppositely-charged leptons (e or mu), large missing transverse momentum and at least two jets. Mass reconstruction of heavy quark candidates is performed by assuming that the W boson decay products are nearly collinear. The data are in agreement with Standard Model expectations; a heavy quark with mass less than 350 GeV is excluded at 95% confidence level.
Search For Standard Model Top Quark And Z Boson Associated Production At Atlas
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Author : Bradley D. Schoenrock
language : en
Publisher:
Release Date : 2016
Search For Standard Model Top Quark And Z Boson Associated Production At Atlas written by Bradley D. Schoenrock 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.
Search For Vector Like T Quarks Using Events With Oppositely Charged Lepton Pairs And Jets In Proton Proton Collisions At Centre Of Mass Energy Of 13 Tev With Cms Detector
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Author : Dalath Rachitha Asanga Mendis
language : en
Publisher:
Release Date : 2019
Search For Vector Like T Quarks Using Events With Oppositely Charged Lepton Pairs And Jets In Proton Proton Collisions At Centre Of Mass Energy Of 13 Tev With Cms Detector written by Dalath Rachitha Asanga Mendis and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
A search is performed for heavy vector-like top quark partner (T) with electric charge +2/3 by using proton-proton collision events from Large Hadron Collider (LHC) at a centre- of-mass energy of 13 TeV. The data corresponds to an integrated luminosity of 35.9fb−1 collected by the Compact Muon Solenoid (CMS) experiment during 2016. The production of this new hypothetical particle is assumed to be in pairs and strong interaction is responsible for such production mechanism. T quarks can decay to various combinations of third generation quarks and standard model bosons: T → bW, tZ, or tH, and hence the final states consist of pair of opposite-sign leptons consistent with coming from a Z boson and jets. No significant excess has been observed and hence 95% CL upper limits are obtained on TT production cross section by assuming different branching ratios. T quark mass values below 1280 GeV are excluded in case of 100% branching fraction for T → tZ.
Searches For Supersymmetric Partners Of The Bottom And Top Quarks With The Atlas Detector
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Author : Alexandru Dafinca
language : en
Publisher:
Release Date : 2014
Searches For Supersymmetric Partners Of The Bottom And Top Quarks With The Atlas Detector written by Alexandru Dafinca and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.