No abstract

We examine in detail radiative corrections to the lightest scalar Higgs boson mass due to the top-quark and top-scalar-quark loops in the next-to-minimal supersymmetric standard model (NMSSM). In our analysis, the mass matrix of the top-scalar-quark contains terms proportional to the gauge couplings. Therefore, our formula for the scalar Higgs boson mass matrix at the 1-loop level partially includes the gauge boson contributions. Thus we calculate the upper bound on the lightest scalar Higgs boson mass without the gauge terms as well as with the gauge terms in the top-scalar-quark masses. The upper bound on the lightest scalar Higgs boson mass can be increased by about 20 GeV by the inclusion of terms proportional to the gauge couplings in the top-scalar-quark masses. We find that the absolute upper bound on the 1-loop corrected mass of the lightest scalar Higgs boson partially including the gauge boson contributions is about 156 GeV.

The renormalization group equations of the Higgs sector of the minimal nonlinear supersymmetric SU(5) model are derived and numerically solved in the scheme. Evolving the parameters of the model from the GUT scale down to the electroweak scale, the allowed regions of the parameters are determined, in particular the quartic coupling constant λ. The mass bounds, corrections to tree-level mass sum rules and productions of the Higgs bosons at e+e− colliders are investigated for the c.m. energy of LEP1, LEP2 and future linear colliders up to 2000 GeV.

We construct a realistic nonlinear supersymmetric Sº(5) model without superpartner particles in curved space and investigate the Higgs sector in the limit of flat space. We need at least an adjoint-, a quintuplet-and an antiquintuplet-Higgs multiplet. In order to obtain a realistic breakdown of Sº(5) to Sº(3);º(1) at tree level we have to modify the vacuum structure of the adjoint representation in comparison to other Sº(5)-models. This model requires an ''elegant'' fine-tuning. We determine the mass spectrum of the electroweak Higgs sector.