2-3 symmetry: Flavor changingb,τdecays, and neutrino mixing

Abstract

The observed pattern of neutrino mixing may be the result of a 2-3$(\ensuremath{\mu}\ensuremath{-}\ensuremath{\tau})$ 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 flavor changing neutral currents in the quark sector and the charged lepton sector that are suppressed by ${m}_{s}/{m}_{b}$ and ${m}_{\ensuremath{\mu}}/{m}_{\ensuremath{\tau}}$ in addition to the mass of the heavy Higgs boson of the second Higgs doublet. A Higgs boson mass of ${m}_{H}\ensuremath{\sim}600--900\text{ }\text{ }\mathrm{GeV}$ can explain the deviation from the standard model reported in several rare $B$ decays. Predictions for other $B$ decays are made, and a new $CP$ phase is predicted in ${B}_{s}\ensuremath{-}{\overline{B}}_{s}$ mixing. The lepton flavor violating decays $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}\overline{l}(\overline{q})l(q)$ 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 $\ensuremath{\sim}2$ degrees.