Lepton-quark symmetry, CP-violation and the decay μ→eγ

If one attempts to understand a dynamical basis for fundamental properties such as the lepton-quark symmetry and parity violation, it appears that one needs in general several exotic gauge bosons. We discuss the phenomenological implications of those presumably massive bosons on CP-violation and the decay μ→eγ. We first consider the exotic gauge doublet (Y+, Y0) appearing in the vector-like SU(6) model discussed by Inoue et al., which realizes the ordinary 4-quarks and 4-leptons as 15-plet representations of SU(6). As is shown, this SU(6) scheme allows a relatively simple model of sub-quarks and sub-leptons, and it is useful as a means to find relevant Feynman rules. We find that CP-violation induced by those exotic bosons (Y+, Y0) approximately reproduces the results of the superweak theory in the K0 sector, provided that the OZI rule and the ΔI=1/2 enhancement are explained in the ordinary 4-quark model. The electric dipole moment D of the neutron is small D/e<=10-27 cm. A reasonable estimate of the exotic decays of the muon is GAMMA(μ→eγ)/GAMMA(μ→all)<=10-13 and GAMMA(μ→eee)/GAMMA(μ→all)<=10-10. We also comment on the implications of the lepto-quark bosons appearing in the fractional charge version of the Pati-Salam model. In a light quark model with only four flavors, we estimate GAMMA(μ→eγ)/GAMMA(μ→all)<=10-11. (auth.)