Hierarchical Fermion Spectra and the KM matrix in Superstring Theories

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The characteristic features of many low-energy parameters have long been a challenging problem to explain their origin from the supersymmetric unified theory. Among them supersymmetric parameters have hierarchical structure. From the viewpoint of the superstring theory we found that Yukawa hierarchies are attributable to the flavor symmetry which stems from the symmetric structure of compactified space. As a result of statemixings we obtained hierachical fermion spectra and the KM matrices for quarks and leptons, which are consistent with the observations. In the KM matrix of leptons seesaw machanism and hierarchical Majorana masses play an essential role. SUSY breaking parameters which are expected to be universal, are closely linked to the mediation mechanism of SUSY breaking. A original model of the mediation has contained serious difficulties. We proposed a new type of mediation model in which the low-energy effective theory is properly derived from the underlying theory and difficulties in the original model are solved. Furthermore, we studied the next-to-minimal supersymmetric standard model in which a gauge-singlet is involved and spontaneous CP violation occurs.