Study of supersymmetric unified theory based on superstring theory

从不同的角度研究了超弦低能有效理论导出的有效超对称模型的唯象特征。本课题取得的主要成果如下：1.具有额外U（1）对称性和规范单态场的模型可以解决最小超对称标准模型（MSSM）中的μ问题。在这类模型中，一个中性伴子扇区被一个额外的U（1）高真和一个费米子伙伴的单重标量所扩展。典型的例子有中性伴子的衰变、电子的电偶极矩和μ * e γ。我们已经分析了这些过程，考虑到动力学项混合的U（1）gauginos，并表明可能有实质性的差异，从MSSM的结果。在适当的条件下，我们可以在额外U（1）的模型中实现小质量的中微子。在这类模型中，Yukawa耦合的群论约束不是很强，因此中微子质量矩阵可以被看作是一个非线性方程。 ...更多信息 与通常的大统一模型有很大不同的结构。在假设存在三个右手中微子和一个很重的右手中微子与其他轻中微子混合的情况下，我们构造了一个唯象中微子质量矩阵。我们已经证明，在这个模型中，太阳和大气中微子的赤字和暗物质问题都可以解释。我们还分析了该模型与原始核合成和其他中微子振荡实验的关系.为了知道带有额外U（1）的模型是否能解决μ问题，我们需要分析在电弱尺度下同时满足电弱相互作用的精确测量和辐射对称性破缺的约束的参数区域的存在性。我们研究了U（1）规范场之间动力学项混合的影响，并指出我们可以找到这样一个参数区域。少

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