Tri-bimaximal neutrino mixing from A4 and θ13 ∼ θC

It is a common believe that, if the tri-bimaximal mixing (TBM) pattern is explained by vacuum alignment in an A(4) model, only a very small reactor angle, say theta(13) similar to O(lambda(2)(C)) being lambda(C) theta(C) the Cabibbo angle, can be accommodated. This statement is based on the assumption that all the flavon fields acquire VEVs at a very similar scale and the departures from exact TBM arise at the same perturbation level. From the experimental point of view, however, a relatively large value theta(13) similar to O(lambda(C)) is not yet excluded by present data. In this paper, we propose a seesaw A4 model in which the previous assumption Call naturally be evaded. The aim is to describe it theta(13) similar to O(lambda(C)) without Conflicting with the TBM prediction for theta(12) which is rather close to the observed value (at lambda(2)(C) level). In our model the deviation of the atmospherical angle from maximal is subject to the sum-rule: sin(2)theta(23) approximate to 1/2 + root 2/2cos delta sin theta(13) which is a next-to-leading order prediction of our model. (c) 2009 Elsevier B.V. All rights reserved.