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.authorChiu, Justin
dc.contributor.supervisorLefebvre, Michel
dc.date.accessioned2020-12-23T06:20:37Z
dc.date.available2020-12-23T06:20:37Z
dc.date.copyright2020en_US
dc.date.issued2020-12-22
dc.degree.departmentDepartment of Physics and Astronomyen_US
dc.degree.levelDoctor of Philosophy Ph.D.en_US
dc.description.abstractThis 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.description.scholarlevelGraduateen_US
dc.identifier.urihttp://hdl.handle.net/1828/12490
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectdark sectoren_US
dc.subjectdark photonen_US
dc.subjectATLASen_US
dc.subjectLHCen_US
dc.subjectHiggs bosonen_US
dc.subjectHiggsen_US
dc.subjectBSMen_US
dc.subjectSMen_US
dc.subjectStandard Modelen_US
dc.subjectbeyond the Standard Modelen_US
dc.subjectsearchen_US
dc.subjectZden_US
dc.subjectZdarken_US
dc.subjectLarge Hadron Collideren_US
dc.subjectelectronsen_US
dc.subjectmuonsen_US
dc.subjectHiggs decaysen_US
dc.subjecthidden sectoren_US
dc.subjectkinetic mixingen_US
dc.subjectHiggs mixingen_US
dc.subjectU(1)en_US
dc.subjecthyperchargeen_US
dc.subjectHiggs portalen_US
dc.subjectdark matteren_US
dc.subjectsymmetry breakingen_US
dc.subjectdata-drivenen_US
dc.subjectfake backgrounden_US
dc.subjectZ_den_US
dc.subjectdetectoren_US
dc.subjectparticle physicsen_US
dc.subjecthepen_US
dc.subjecthep-exen_US
dc.subjecthigh energy physicsen_US
dc.subjectCERNen_US
dc.subjectrun-2en_US
dc.subjectfake factoren_US
dc.titleSearch for Higgs boson decays to beyond-the-Standard-Model light bosons in four-lepton events with the ATLAS detector at the LHCen_US
dc.typeThesisen_US

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