We study Higgs boson phenomenology in two different extensions of the standard model (SM): the minimal supersymmetric extension of the SM and a new dynamical symmetry breaking model with a fundamental Higgs boson.
First, we present a comprehensive analysis on the MSSM Higgs sector CP violation at photon colliders including the chargino contribution as well as the contributions of the other charged particles. In most supersymmetric theories, charginos $\widetilde{X}^{\pm}_{1,2}$ belong to the class of the lightest supersymmetric particles and the couplings of Higgs bosons to charginos are in general complex so that the CP--violating chargino contributions to the loop--induced coupling of the Higgs bosons to photon pairs can be important, which can also be sizable for the lightest Higgs boson even in the decoupling limit of large pseudoscalar mass mA with only the lightest Higgs boson kinematically accessible at future high energy colliders. Polarization asymmetries are indispensable in determining the CP properties of neutral Higgs bosons.
In the extra dimensional scenarios with gauge fields in the bulk, the Kaluza-Klein (KK) gauge bosons can induce Nambu-Jona-Lasinio (NJL) type attractive four-fermion interactions, which can break electroweak symmetry dynamically with accompanying composite Higgs fields. Largely motivated by this observation, we consider a simple model where electroweak symmetry breaking (EWSB) is triggered by both a fundamental Higgs and a composite Higgs arising in a dynamical symmetry breaking mechanism induced by a new strong dynamics. The resulting Higgs sector is a partially composite two-Higgs doublet model with specific boundary conditions on the coupling and mass parameters originating at a compositeness scale Λ. The phenomenology of this model is discussed including the collider phenomenology at LHC and ILC.
