Revisiting bimaximal neutrino mixing in a model with S-4 discretesymmetry

Abstract

In view of the fact that the data on neutrino mixing are stillcompatible with a situation where Bimaximal mixing is valid in firstapproximation and it is then corrected by terms of O(lambda(C)) (withlambda(C) being the Cabibbo angle), arising from the diagonalization ofthe charged lepton masses, such that delta sin(2)theta(12) similar tosin theta(13) similar to O(lambda(C)) while delta sin(2)theta(23)similar to O(lambda(2)(C)), we construct a model based on the discretegroup S 4 where those properties are naturally realized. The model issupersymmetric in 4-dimensions and the complete flavour group is S-4 xZ(4) x U(1)(FN), which also allows to reproduce the hierarchy of thecharged lepton spectrum. The only fine tuning needed in the model is toreproduce the small observed value of r = Delta m(sun)(2)/Deltam(atm)(2). Once the relevant parameters are set to accommodate r thenthe spectrum of light neutrinos shows a moderate normal hierarchy andis compatible, within large ambiguities, with the constraints fromleptogenesis as an explanation of the baryon asymmetry in the Universe.