ar X iv : h ep - p h / 05 08 31 4 v 3 2 3 N ov 2 00 5 The 2 - 3 symmetry : Flavor Changing b , τ Decays and Neutrino Mixing

The observed pattern of neutrino mixing may be the result of a 2-3( μ−τ) symmetry in the leptonic sector. We consider a two Higgs doublet model with a 2-3 symmetry in the down type quark and the charged lepton sector. The breaking of the 2-3 symmetry by the strange quark mass and the muon mass leads to FCNC in the quark sector and the charged lepton sector that are suppressed by ms mb and mμ mτ in addition to the mass of the heavy Higgs boson of the second Higgs doublet. A Higgs boson mass of mH ∼ 600−900 GeV can explain the deviation from standard model reported in several rare B decays. Predictions for other B decays are made and a new CP phase is predicted in Bs − B̄s mixing. The lepton flavour violating decays τ → μl̄(q̄)l(q) are below the experimental limits. The breaking of 2-3 symmetry in the lepton sector can lead to deviations of the atmospheric neutrino mixing angle from the maximal value by ∼ 2 degrees. [email protected] [email protected]