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Title:First evidence for vector boson fusion produced Higgs boson in the WW* decay channel and search for extended Higgs sector
Author(s):Chang, Philip Choong
Director of Research:Neubauer, Mark S
Doctoral Committee Chair(s):Pitts, Kevin T
Doctoral Committee Member(s):Willenbrock, Scott S; Fields, Brian D
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):LHC, Large Hadron Collider, Higgs boson, Higgs sector,
Abstract:The discovery of a new boson state in 2012 shook the field of particle physics. The subsequent measurements of the properties of the newly found particle led to the conclusion that the particle is consistent the Standard Model Higgs boson within the uncertainty of the measurements. Individual observations of the Higgs boson production and decay channels are crucial in further confirming beyond a doubt that this is indeed the Standard Model Higgs boson. This thesis presents the first evidence for the vector boson fusion (VBF) produced Higgs boson in exclusive Higgs boson decay channel (H → WW∗). The best single channel constraint on the fermionic coupling of the Higgs boson comes from the measurement presented in the thesis. The analysis is performed using an integrated luminosity of 25 fb^−1 from √s = 7 and 8 TeV pp collision data recorded by the ATLAS detector at the LHC. The observed (expected) significance for the vector boson fusion produced H→WW∗ is 3.2 (2.7) standard deviations. As the existence of the Higgs sector is established, using the Higgs boson as a tool, a strategy for a non-Standard Model decay of the Higgs boson H → ss → bbμμ is documented in this thesis, where s is a hypothetical (pseudo)scalar with connections to Dark Matter mod- els. The strategy has been tested using data with an integrated luminosity of 36 fb^−1 from √s = 13 TeV pp collisions recorded by the ATLAS detector and the sensitivity of the channel is analyzed. The expected upper limit on the branching ratio is found to be B(H → bbμμ) ≤ 2.4 − 4.8 × 10^−4 at 95% confidence limit across the mass range of 20 GeV < m_s < 60 GeV.
Issue Date:2017-02-24
Rights Information:Copyright 2017 Philip Chang
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05

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