| Summary: | 博士 === 國立中央大學 === 物理學系 === 106 === We review the basics of the Higgs sector, the electroweak sector and the Yukawa sector in the Georgi-Machacek (GM) model, theoretical constraints of the vacuum stability and perturbative unitarity, both at tree level, and indirect experimental constraints, such as the oblique corrections, the Zbb vertex, and 125-GeV Higgs signal strengths. The decay of the Higgs bosons both at tree level and 1-loop level are also discussed.
Current CERN Large Hadron Colllider (LHC) data on the 125 GeV standard model-like Higgs boson suggest the possibility of larger Higgs boson couplings with the weak gauge bosons, g_{hVV}, than those in the standard model (SM). We use the GM model as an explicit model to realize such a scenario. We find that g_{hVV} couplings can be larger than the SM value by a factor of about 1.3 maximally in the parameter region consistent with the current Higgs boson search data and allowed by various other constraints. We then show how the modified g_{hVV} couplings lead to enhancements in various weak boson scattering processes. This can be clearly observed as excesses in the transverse mass distributions at around 125 GeV and also the mass of heavy Higgs bosons.
We then derive the mose general sets of viable mass spectra of the exotic Higgs bosons in the GM model that are allowed by the above-mentioned constraints. Branching ratios of various cascade decay channels of the doubly-charged Higgs boson in the 5 representation, the singly-charged Higgs boson in 3 and the singlet Higgs boson are further computed. As one of the most promising channels for discovering the model, we study the prospects for detecting the doubly-charged Higgs boson that is produced via the vector boson fusion process and decays into final states containing a pair of same-sign leptons at the 14-TeV LHC and a 100-TeV future pp collider. For this purpose, we evaluate acceptance times efficiency for signals of the doubly-charged Higgs boson with general viable mass spectra and compare it with the SM background estimates.
Finally, we calculate 1-loop radiative corrections to the hZZ, hWW, hff and hhh couplings in the GM model. A comparison of the 1-loop radiative corrected hZZ and hWW couplings in the models with next-to-simplest Higgs sectors satisfying the electroweak rho parameter equal to 1 at tree level: the real Higgs singlet model, the two-Higgs doublet models, and the Georgi-Machacek model, is given. Under theoretical and current experimental constraints, the three models have different correlations between the deviations in the hZZ and hWW couplings from the standard model predictions. In particular, we find for each model predictions with no overlap with the other two models.
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