Hybrid seesaw neutrino masses with A4 family symmetry

We consider the scenario in which neutrino data are explained by the interplay of type I and II seesaw terms in the Majorana neutrino mass matrix Mu(v) = Mu(L) - MDMR-1 M-D(T). We construct a predictive model with Mu L proportional to the unit matrix, 3 diagonal texture zeros in Mu(R), and Mu(D) diagonal. We show how this pattern can be maintained by the non-Abelian discrete symmetry A(4), and discuss its phenomenological consequences. It turns out that the two types of seesaw give contributions of the same order to M-v. In the CP conserving case, we find sin theta(13) approximate to 2/(tan 2 theta(23) tan 2 theta(12)) and we predict inverted (normal) ordering of the mass spectrum for tan(2) theta(12) < 0.5 (> 0.5). (c) 2005 Elsevier B.V. All rights reserved.