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The Search for new Resonances in Strong Symmetry Breaking Scenarios with the ATLAS Detector

Using the most recent data collected by the ATLAS detector in pp collisions delivered by the LHC at 7 and 8 TeV, this thesis shall establish severe constraints on a variety of models going beyond the Standard Model (SM) of particle physics. More particularly, two types of hypothetical particles, exi...

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Autor principal: Davies, Merlin
Lenguaje:eng
Publicado: 2014
Materias:
Acceso en línea:http://cds.cern.ch/record/1707903
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author Davies, Merlin
author_facet Davies, Merlin
author_sort Davies, Merlin
collection CERN
description Using the most recent data collected by the ATLAS detector in pp collisions delivered by the LHC at 7 and 8 TeV, this thesis shall establish severe constraints on a variety of models going beyond the Standard Model (SM) of particle physics. More particularly, two types of hypothetical particles, existing in various theoretical models shall be studied and probed. The first type will be the search for vector-like quarks (VLQ) produced in pp collisions through electroweak couplings with the u and d quarks. The quest for these particles will be made as they decay into either $W(\ell\nu)$+jet or $Z(\ell\ell)$+jet. There exist theoretical arguments that establish that, under certain reasonable conditions, single production of VLQ dominates over production in pairs. The particular topology of such events enables the implementation of effective techniques to extract signal over electroweak background. The second type is the search for resonant particles decaying to $WZ$ when the gauge bosons $W$ and $Z$ decay leptonically. The final states detected by ATLAS therefore contain three leptons (e, or $\mu$) and missing transverse energy. The distribution of the invariant mass of these objects will then be examined to determine the presence or absence of new resonances that manifest themselves as localized excesses in $m(WZ)$. Despite the fact that, at first glance, these two new types of particles have very little in common, they are in fact both closely linked to electroweak symmetry breaking. In many theoretical models, the hypothetical existence of VLQ is put forward to counteract the top quark’s contribution to radiative loop corrections of the Higgs mass, a calculation which assumes that the Higgs is an elementary particle. Concurrently, other models foretelling the existence $WZ$ resonances alternatively suggest that the Higgs is a composite particle, completely rewriting the whole Higgs sector of the SM. In this perspective, the two analyses presented in this thesis have a fundamental link with the very nature of the Higgs, thereby extending our knowledge of the origin of particle masses. Ultimately, the two analyses did not observe any significant excess in their respective signal regions, paving the way for the computations of limits on the production cross section as a function of the mass of the resonances.
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spelling cern-17079032019-09-30T06:29:59Zhttp://cds.cern.ch/record/1707903engDavies, MerlinThe Search for new Resonances in Strong Symmetry Breaking Scenarios with the ATLAS DetectorParticle Physics - ExperimentUsing the most recent data collected by the ATLAS detector in pp collisions delivered by the LHC at 7 and 8 TeV, this thesis shall establish severe constraints on a variety of models going beyond the Standard Model (SM) of particle physics. More particularly, two types of hypothetical particles, existing in various theoretical models shall be studied and probed. The first type will be the search for vector-like quarks (VLQ) produced in pp collisions through electroweak couplings with the u and d quarks. The quest for these particles will be made as they decay into either $W(\ell\nu)$+jet or $Z(\ell\ell)$+jet. There exist theoretical arguments that establish that, under certain reasonable conditions, single production of VLQ dominates over production in pairs. The particular topology of such events enables the implementation of effective techniques to extract signal over electroweak background. The second type is the search for resonant particles decaying to $WZ$ when the gauge bosons $W$ and $Z$ decay leptonically. The final states detected by ATLAS therefore contain three leptons (e, or $\mu$) and missing transverse energy. The distribution of the invariant mass of these objects will then be examined to determine the presence or absence of new resonances that manifest themselves as localized excesses in $m(WZ)$. Despite the fact that, at first glance, these two new types of particles have very little in common, they are in fact both closely linked to electroweak symmetry breaking. In many theoretical models, the hypothetical existence of VLQ is put forward to counteract the top quark’s contribution to radiative loop corrections of the Higgs mass, a calculation which assumes that the Higgs is an elementary particle. Concurrently, other models foretelling the existence $WZ$ resonances alternatively suggest that the Higgs is a composite particle, completely rewriting the whole Higgs sector of the SM. In this perspective, the two analyses presented in this thesis have a fundamental link with the very nature of the Higgs, thereby extending our knowledge of the origin of particle masses. Ultimately, the two analyses did not observe any significant excess in their respective signal regions, paving the way for the computations of limits on the production cross section as a function of the mass of the resonances.CERN-THESIS-2013-323oai:cds.cern.ch:17079032014-06-09T20:34:43Z
spellingShingle Particle Physics - Experiment
Davies, Merlin
The Search for new Resonances in Strong Symmetry Breaking Scenarios with the ATLAS Detector
title The Search for new Resonances in Strong Symmetry Breaking Scenarios with the ATLAS Detector
title_full The Search for new Resonances in Strong Symmetry Breaking Scenarios with the ATLAS Detector
title_fullStr The Search for new Resonances in Strong Symmetry Breaking Scenarios with the ATLAS Detector
title_full_unstemmed The Search for new Resonances in Strong Symmetry Breaking Scenarios with the ATLAS Detector
title_short The Search for new Resonances in Strong Symmetry Breaking Scenarios with the ATLAS Detector
title_sort search for new resonances in strong symmetry breaking scenarios with the atlas detector
topic Particle Physics - Experiment
url http://cds.cern.ch/record/1707903
work_keys_str_mv AT daviesmerlin thesearchfornewresonancesinstrongsymmetrybreakingscenarioswiththeatlasdetector
AT daviesmerlin searchfornewresonancesinstrongsymmetrybreakingscenarioswiththeatlasdetector