Cancellation Mechanism of FCNCs in S_4 x Z_2 Flavor Symmetric Extra U(1) Model

Abstract

We propose a E_6 inspired supersymmetric model with a non-Abelian discrete flavor symmetry; SU(3)_c x SU(2)_W x U(1)_Y x U(1)_X x S_4 x Z_2. In our scenario, the additional abelian gauge symmetry; U(1)_X, not only solves the mu-problem in the minimal Supersymmetric Standard Model(MSSM), but also requires new exotic fields which play an important role in solving flavor puzzles. If our exotic quarks can be embedded into a S_4 triplet, which corresponds to the number of the generation, one finds that dangerous proton decay can be well-suppressed. Hence, it might be expected that the generation structure for lepton and quark in the SM(Standard Model) can be understood as a new system in order to stabilize the proton in a supersymemtric standard model (SUSY). Moreover, due to the nature of the discrete non-Abelian symmetry itself, Yukawa coupling constants of our model are drastically reduced. In our previous work, we actually have found much success. However, we also have to solve Higgs mediated FCNC at tree level, as is often the case with such extended Higgs models. In this paper, we propose a promising mechanism which could make cancellation between Higgs and SUSY contributions.Comment: 19 pages, 2 tables, no figures. Title is slightly changed and minor parts are modifie