Underlying A4 symmetry for the neutrino mass matrix and the quark mixing matrix

The discrete non-Abelian symmetry A(4), valid at some high-energy scale, naturally leads to three degenerate neutrino masses, without spoiling the hierarchy of charged-lepton masses. Realistic neutrino mixing angles (one of which is necessarily maximal and the other large) are then automatically induced radiatively, and the correct mass splittings may be obtained in the context of softly broken supersymmetry. The quark mixing matrix is also calculable in a similar way. The mixing parameter U-e3 is predicted to be imaginary, leading to maximal CP violation in neutrino oscillations. Neutrinoless double beta decay and tau --> muy should be in the experimentally accessible range. (C) 2002 Elsevier Science B.V. All rights reserved.