
内容記述 
In the Standard Model (SM) of particle physics, the Higgs sector is introduced in order to explain the mass of gauge bosons and fermions without conflict with the gauge principle. In the Higgs sector, the Higgs field φ, which have a nonzero vacuum expectation value, is introduced, and then the existence of Higgs boson is predicted. After the discovery of the top quark, the Higgs sector is the last remaining part yet to be confirmed in the SM. Experimental search for the Higgs boson has been continued at the Fermilab Tevatron experiments and will be succeeded by the CERN Large Hadron Collider (LHC) and future linear colliders (LC's). Discovery of the Higgs boson is important not only in confirming the mechanism of the electroweak gaugesymmetry breaking but also in providing us useful information on physics beyond the SM. As such a physics, some models are proposed. For each model, allowed properties of the Higgs boson is obtained. When the Higgs boson is discovered, its mass and various decay properties will be measured to test the SM and to distinguish models of new physics at high energy scales. In this thesis we obtain allowed properties of the Higgs boson theoretically in various extensions of the SM, e.g. twoHiggsdoublet model (2HDM) with a softlybroken discrete symmetry, ZeeModel which requires the existence of a SU (2) charged Higgs singlet in order to generate the small neutrino mass, and Minimal supersymmetric Standard Model (MSSM).<br /><br /> The most interesting property of the Higgs boson is its mass value. Although the mass of the Higgs boson is a free parameter in the SM, we can obtain its mass bounds by demanding the considered theory to be a valid effective theory all the way up to some cutoff energy scale (Λ); if we require the vacuum stability and the validity of perturbation theory below a given cutoff scale Λ, we can determine the lower and the upper bounds of the Higgs boson mass as a function of Λ, respectively, using renormalization group equations (RGE's). In the SM, for the Planck scale m<SUB>p1</SUB>～10<SUP>19</SUP> GeV as Λ, the lower and the upper bounds become about 145 and 175 GeV at m<SUB>t</SUB>＝175 GeV, respectively.<br /><br /> In the MSSM which is the most popular in the particle models beyond the SM, the theoretical upper bound on the lightest CPeven Higgs boson mass is given by about 120 GeV for m<SUB>t</SUB>＝175 GeV and m<SUB>stop</SUB>＝1 TeV.<br /><br /> The lightest CPeven Higgsboson mass for the 2HDM is investigated. This model includes one more Higgs doublet compared to the SM Higgs sector. This is the most simple extension of the SM. Through spontaneous symmetry breaking, five physical Higgs bosons appear, i.e. two CPeven, one CPodd and a pairs of charged Higgs bosons. In the 2HDM, the mass upper bound is the same as that of the SM, whereas the lower bound is reduced to zero. Specially, in the decoupling regime, where only one neutral Higgs boson is light as compared to the other physical states of Higgs bosons, the lower bound of the lightest Higgs boson mass is given by 100 GeV for Λ＝10<SUP>19</SUP> GeV and m<SUB>t</SUB>＝175 GeV. This is considerably smaller as compared to the SM value.<br /><br /> Next, the Higgs boson mass bounds for the ZeeModel is investigated. From the observations of atmospheric and solar neutrinos, there are increasing evidences for neutrino oscillations. If this is a correct interpretation, the SM has to be extended to incorporate the small masses of the neutrinos suggested by data. There has been several ideas proposed in literature to generate small neutrino masses. The Zeemodel is one of such attempts. In this model, the three different flavor neutrinos are massless at the tree level, and their small masses are induced radiatively through oneloop diagrams. For such a massgeneration mechanism to work, it is necessary to extend the Higgs sector of the SM to contain at least two weakdoublet fields and one weaksinglet charged scalar field. The Higgs sector of the Zeemodel is similar to that of the 2HDM except for the existence of an additional weaksinglet charged Higgs field, so that the physical scalarbosons include two CPeven, one CPodd and two pairs of charged Higgs bosons. We show that the mass bounds for the lightest CPeven Higgs boson are almost the same as those in the 2HDM.<br /><br /> For the ZeeModel, although the allowed mass range is the same as that of the 2HDM, other properties can be different from that in the usual Higgs doublet model. We examine effects of the additional loop contribution of the singlet charged Higgs boson to the partial decay width of h→γγ. If we assume Λ＝10<SUP>19</SUP> GeV, the deviation of the decay width from the SM prediction can be about 20% within the allowed range of the Higgs selfcoupling constants which is obtained by the RGE analysis. This amount of deviation could be tested at the future LC or photonphoton LC experiments. We also discuss phenomenology of the singlet charged Higgs boson at present and future collider experiments, which is found to be completely different from that of the ordinary 2HDMlike charged Higgs bosons. 