Lepton flavour violation in models with A(4) flavour symmetry

We analyze lepton flavour violating transitions, leptonic magnetic dipole moments (MDMs) and electric dipole moments (EDMs) in a class of models characterized by the flavour symmetry A(4) x Z(3) x U(1)(FN), whose choice is motivated by the approximate tri-bimaximal mixing observed in neutrino oscillations. We construct the relevant low-energy effective Lagrangian where these effects are dominated by dimension six operators. suppressed by the scale M of new physics. All the flavour breaking effects are universally described by the vacuum expectation values of a set of spurions. We separately analyze both a supersymmetric and a general case. While the observed discrepancy delta a(mu) in the anomalous MDM of the muon suggests M of order of a few TeV, several data require M above 10 TeV, in particular the limit on EDM of the electron. In the general case also the present limit on BR(mu -> e gamma) requires M > 10 TeV, at least. The branching ratios for mu -> e gamma, tau -> mu gamma and tau -> e gamma are all expected to be of the same order. In the supersymmetric case the constraint from mu -> e gamma is softened and it can be satisfied by a smaller scale M. In this case both the observed delta a(mu) and the current bound on BR(mu -> e gamma) can be satisfied, at the price of a rather small value for ||, of the order of a few pet-cents, that reflects on a similar value for theta(13). (C) 2008 Elsevier B.V. All rights reserved.