Phenomenology in the Zee Model with the A4 Symmetry
Abstract
The Zee model generates neutrino masses at the one-loop level by adding charged SU(2)L-singlet and extra SU(2)L-doublet scalars to the standard model of particle physics. As the origin of the nontrivial structure of the lepton flavor mixing, we introduce the softly broken A4 symmetry to the Zee model. This model is compatible with the tribimaximal mixing which agrees well with neutrino oscillation measurements. Then, a sum rule m1 ei alpha12 + 2 m2 + 3 m3 ei alpha32 = 0 is obtained and it results in Delta m231 < 0 and m3 > 1.8*10-2eV. The effective mass |(Mnu)ee| for the neutrinoless double beta decay is predicted as | (M)ee | > 1.7*10-2eV. The characteristic particles in this model are SU(2)L-singlet charged Higgs bosons s+alpha (alpha=xi,eta,zeta) which are made from a 3-representation of A4. Contributions of s+alpha to the lepton flavor violating decays of charged leptons are almost forbidden by an approximately remaining Z3 symmetry; only BR(tau to ebar mu mu) can be sizable by the flavor changing neutral current interaction with SU(2)L-doublet scalars. Therefore, s+alpha can be easily light enough to be discovered at the LHC with satisfying current constraints. The flavor structures of BR(s-alpha to ell nu) are also discussed.