Study of supersymmetric unified theory based on superstring theory

点击翻译按钮获取中文摘要

Phenomenological features of effective supersymmetric models derived as the low energy effective theory of superstring have been studied from various points of view. Main results obtained in this project are followings.1. Models with an extra U (1) symmetry and a gauge singlet field can solve a mu-problem in the minimal supersymmetric standard model (MSSM). In this kind of models a neutralino sector is extended by an extra U (1) gaugino and a fermion partner of the singlet scalar. There can appear typical examples are decays of neutralinos, an electric dipole moment of an electron and mu*egamma. We have analyzed these processes taking account of a kinetic term mixing of U (1) gauginos and shown that there could be substantial differences from the MSSM results.2. We can realize small neutrino masses under a suitable condition in the models with an extra U (1). In this type of models group theoretical constraints on Yukawa couplings are not so strong and then a neutrino mass matrix can h … More ave a largely different structure from the one of usual grand unified models. Under assumptions of the existence of three right-handed neutrinos and mixings between a very heavy right-handed neutrino and other light neutrinos, we have constructed a phenomenological neutrino mass matrix. We have shown that in this model both deficits of solar and atmospheric neutrinos and the dark matter problem could be explained. We have also analyzed the relation of this model to the primordial nucleosynthesis and other neutrino oscillation experiments.3. In order to know whether the models with an extra U (1) can solve the mu-problem or not, we need to analyze the existence of the parameter region which satisfys both constraints from prescise measurements of the electroweak interaction and the radiative symmetry breaking at the electroweak scale. We have studied this subject taking account of an effect of the kinetic term mixing among U (1) gauge fields and shown that we could find such an parameter region. Less