Search for Higgs boson decays to beyond-the-Standard-Model light bosons in four-lepton events with the ATLAS detector at the LHC

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dc.contributor.author Chiu, Justin
dc.date.accessioned 2020-12-23T06:20:37Z
dc.date.available 2020-12-23T06:20:37Z
dc.date.copyright 2020 en_US
dc.date.issued 2020-12-22
dc.identifier.uri http://hdl.handle.net/1828/12490
dc.description.abstract This thesis presents the search for the dark sector process h -> Zd Zd -> 4l in events collected by the ATLAS detector at the Large Hadron Collider in 2015--2018. In this theorized process, the Standard Model Higgs boson (h) decays to four leptons via two intermediate Beyond-the-Standard-Model particles each called Zd. This process arises from interactions of the Standard Model with a dark sector. A dark sector consists of one or more new particles that have limited or zero interaction with the Standard Model, such as the new vector boson Zd (dark photon). It could have a rich and interesting phenomenology like the visible sector (the Standard Model) and could naturally address many outstanding problems in particle physics. For example, it could contain a particle candidate for dark matter. In particular, Higgs decays to Beyond-the-Standard-Model particles are well-motivated theoretically and are not tightly constrained; current measurements of Standard Model Higgs properties permit the fraction of such decays to be as high as approximately 30%. The results of this search do not show evidence for the existence of the h -> Zd Zd -> 4l process and are therefore interpreted in terms of upper limits on the branching ratio B(h -> Zd Zd) and the effective Higgs mixing parameter kappa^prime. en_US
dc.language English eng
dc.language.iso en en_US
dc.rights Available to the World Wide Web en_US
dc.subject dark sector en_US
dc.subject dark photon en_US
dc.subject ATLAS en_US
dc.subject LHC en_US
dc.subject Higgs boson en_US
dc.subject Higgs en_US
dc.subject BSM en_US
dc.subject SM en_US
dc.subject Standard Model en_US
dc.subject beyond the Standard Model en_US
dc.subject search en_US
dc.subject Zd en_US
dc.subject Zdark en_US
dc.subject Large Hadron Collider en_US
dc.subject electrons en_US
dc.subject muons en_US
dc.subject Higgs decays en_US
dc.subject hidden sector en_US
dc.subject kinetic mixing en_US
dc.subject Higgs mixing en_US
dc.subject U(1) en_US
dc.subject hypercharge en_US
dc.subject Higgs portal en_US
dc.subject dark matter en_US
dc.subject symmetry breaking en_US
dc.subject data-driven en_US
dc.subject fake background en_US
dc.subject Z_d en_US
dc.subject detector en_US
dc.subject particle physics en_US
dc.subject hep en_US
dc.subject hep-ex en_US
dc.subject high energy physics en_US
dc.subject CERN en_US
dc.subject run-2 en_US
dc.subject fake factor en_US
dc.title Search for Higgs boson decays to beyond-the-Standard-Model light bosons in four-lepton events with the ATLAS detector at the LHC en_US
dc.type Thesis en_US
dc.contributor.supervisor Lefebvre, Michel
dc.degree.department Department of Physics and Astronomy en_US
dc.degree.level Doctor of Philosophy Ph.D. en_US
dc.description.scholarlevel Graduate en_US

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