Low-energy Variety of Asymmetric SUSY Flavor Structure

In this letter we study the low-energy phenomenology and cosmological implications of supersymmetric grand unified theory with asymmetric flavor structure, which is suggested by the recent observation of fermion masses and mixing angles. The predictions of the scenario are rather dependent on a Yukawa parameter fixed by group-theoretical argument. A reduced value of the parameter gives a resolution to the sign problem of supersymmetric Higgs mass μ, with which the theory becomes simultaneously consistent with the experimental data of bottom/tau mass ratio, flavor-changing rare decay of bottom quark, and the muon anomalous magnetic moment. The relic abundance of the lightest superparticle as cold dark matter of the universe is also investigated in light of the three-years WMAP result. A new source of flavor violation is found in the D-term induced scalar masses, that is a distinctive signature of the generation asymmetry. The minimal supersymmetric standard model is conceived to be one of the promising theoretical candidates beyond the standard model for its brevity and attractive features. A remarkable property of supersymmetric standard models is the unification of gauge coupling constants at some high-energy scale [1]. This motivates us to promote it into grand unified theory (GUT) [2] and various attempts have been devoted to constructing realistic models and understanding their phenomenological implications. The quarks and leptons are generally unified into multiplets of GUT gauge group. That seems to conflict with disparate flavor structures, namely the observed fermion masses and mixing angles. For example, the well-known GUT relation between down-quark and chargelepton Yukawa couplings leads to the same mass eigenvalues of quarks and leptons, which is successful only for the third generation. Further if each one-generation matter is combined into a single multiplet, the quark and lepton mixing matrices have similar forms, inconsistent with the experimental observation. Therefore a naive unification hypothesis should be modified in the flavor (Yukawa coupling) sector. Lopsided flavor structure in the generation space is one of promising ways to remedy the flavor difficulties in grand unification. It has recently been shown, for example, that the flavor asymmetry is dynamically realized by introducing matter multiplets in a generation-dependent fashion. With such a experimentally suggested form of flavor couplings, novel behaviors emerge in the electroweak gauge symmetry breaking and the mass spectrum of superparticles. Extending the previous study [3], in this letter we further discuss phenomenological and cosmological issues such as flavor-violating rare processes and the relic dark matter abundance in the universe. In the analysis of this letter, we assume the following general form of Yukawa couplings at the GUT scale, where the electroweak gauge couplings meet: