The A4 flavor symmetry and neutrino phenomenology
Abstract
It has been shown that tribimaximal mixing can be obtained by some particular breaking pattern of the A4 symmetry, wherein the extra A4 triplet Higgs scalars pick up certain fixed vacuum expectation value (VEV) alignments. We have performed a detailed analysis of the different possible neutrino mass matrices within the framework of the A4 model. We take into account all possible singlet and triplet Higgs scalars which leave the Lagrangian invariant under A4. We break A4 spontaneously, allowing the Higgs to take any VEV in general. We show that the neutrino mixing matrix deviates from tribimaximal, both due to the presence of the extra Higgs singlets, as well as from the deviation of the triplet Higgs VEV from its desired alignment, taken previously. We solve the eigenvalue problem for a variety of these illustrative cases and identify the ones where one obtains exact tribimaximal mixing. All such cases require fine-tuning. We show which neutrino mass matrices would be strongly disfavored by the current neutrino data. Finally, we study in detail the phenomenology of the remaining viable mass matrices and establish the deviation of the neutrino mixing from tribimaximal, both analytically as well as numerically.