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Search for New Resonances and Dark Matter Particles with BSM Higgs Boson Productions at the LHC

dc.contributor.authorGuo, Wen
dc.date.accessioned2018-06-07T17:46:32Z
dc.date.availableNO_RESTRICTION
dc.date.available2018-06-07T17:46:32Z
dc.date.issued2018
dc.date.submitted2018
dc.identifier.urihttps://hdl.handle.net/2027.42/144028
dc.description.abstractThis dissertation presents searches for dark matter particles and new resonances at the LHC with the ATLAS experiment. The data used in these analyses are produced in proton-proton collisions at a center-of-mass energy of 13 TeV and are collected by the ATLAS experiment, with a total integrated luminosity of 36.1 fb −1 . The experimental signature of new physics in this work involves large missing transverse energy (ETmiss) plus a di-lepton pair from a Z boson decay. In the dark matter search program, it is hypothesized that the Higgs boson may couple to invisible particles who serve as dark matter candidates. The Higgs boson is produced in association with a Z boson, which is used as a ‘tag’ particle through its charged lepton (ee or μμ) decays. The dark matter signature is large ETmiss since the dark matter particles, just like the neutrinos, escape from the detector (invisible). The challenge of searching for dark matter is to understand sources of ETmiss produced in proton-proton collisions and design an efficient event selection criterion to separate the signal from the backgrounds. Selected data is compared with the expected background and the dark matter signal, assuming the Standard Model (SM) ZH production cross section. Data is found to be consistent with the background expectation. An upper limit on the branching fraction of the Higgs boson decaying to invisible particles of 67% is set at 95% confidence level (CL). The corresponding limits on the production cross-section (σ) of beyond the SM Zh process with the invisible Higgs boson decays are also presented in a mass range of 110 to 400 GeV. The two-Higgs-doublet model and the electroweak singlet model are motivated theoretical models, which predict additional Higgs bosons near the TeV scale that may decay to pairs of Z bosons. The search for these non-SM Higgs bosons are also conducted with di-lepton plus ETmiss final states, but by considering the decay mode ZZ → llνν (l = e, or μ). The transverse mass spectrum of the ll + ETmiss system is used as the discriminant to search for bumps created by new resonances. Comparing data with the expected signal and background, no evidence is found for new resonance production in the mass range between 300 GeV to 1500 GeV. Therefore, the limits on new resonance production cross-section times a branching ratio are set. This result is also interpreted as a search for a spin-2 Kaluza-Klein graviton excitation, G∗KK , in the context of the bulk Randall-Sundrum model via G∗KK → ZZ∗ → llνν process. An upper limit on σ × BR(G∗KK → ZZ∗) is set as a function of the KK graviton mass between 600 GeV and 2 TeV.
dc.language.isoen_US
dc.subjectexperimental high energy physics
dc.subjectdark matter search
dc.subjecthigh mass Higgs
dc.subjectinvisible Higgs boson decay
dc.titleSearch for New Resonances and Dark Matter Particles with BSM Higgs Boson Productions at the LHC
dc.typeThesisen_US
dc.description.thesisdegreenamePhDen_US
dc.description.thesisdegreedisciplinePhysics
dc.description.thesisdegreegrantorUniversity of Michigan, Horace H. Rackham School of Graduate Studies
dc.contributor.committeememberZhou, Bing
dc.contributor.committeememberYang, Qiong
dc.contributor.committeememberAidala, Christine A
dc.contributor.committeememberPierce, Aaron Thomas
dc.contributor.committeememberSchwarz, Thomas Andrew
dc.subject.hlbsecondlevelPhysics
dc.subject.hlbtoplevelScience
dc.description.bitstreamurlhttps://deepblue.lib.umich.edu/bitstream/2027.42/144028/1/wenguo_1.pdf
dc.identifier.orcid0000-0001-7285-7490
dc.identifier.name-orcidGuo, Wen; 0000-0001-7285-7490en_US
dc.owningcollnameDissertations and Theses (Ph.D. and Master's)


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