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Abstract
In the Standard Model, the Higgs boson is responsible for mass-generation and stabilizing the electroweak interaction at high energies. The boson has not been observed and the Standard Model does not predict its mass. Direct searches have excluded the existence of a Higgs boson with a mass less than 113 GeV. Searches to date have focussed on b-quark decays of the Higgs, but the model predicts an increased branching fraction to massive vector boson pairs for a heavier Higgs. In some extensions of the Standard Model which predict multiple Higgs bosons, the lightest Higgs boson couples primarily to bosons, not fermions. Results excluding these “fermiophobic” models have used the two-photon decay to date, but for Higgs masses above 100 GeV, the decay to massive vector boson pairs dominates. In this dissertation, I present the first search for a Higgs boson decaying to massive vector boson pairs. The search is based on data collected by the L3 experiment at CERN during the 1999–2000 period.
The search uses the Higgsstrahlung production mode where the Higgs is radiated from an off-shell Z boson, so the analysis must include the decay of the Z boson as well as the decay of the two W or Z bosons from the Higgs decay. The events will contain six final state fermions, and the decays of the W and Z define nine different channels for the h → WW search. I present the details and results of analyses for six of the channels. The combined analyses exclude a fermiophobic Higgs decaying to massive vector boson pairs for 83.8 GeV < mh</sub> < 104.2 GeV at a 95% confidence level with an unexcluded region between 88.8 GeV < m h</sub> < 89.6 GeV. Monte Carlo predictions of the analyses' performance predict an exclusion range of 86.8 GeV < mh</sub> < 107.5 GeV. I also present model-independent branching ratio limits for the massive vector boson search, as well as a scan of the fermiophobic plane combining with the results of the LEP h → γγ search.
