Perturbing exactly tri-bimaximal neutrino mixings with charged lepton mass matrices

We study perturbations of exactly tri-bimaximal neutrino mixings under the assumption that they are coming solely from the charged lepton mass matrix. This may be plausible in scenarios where the mass generation mechanisms of neutrinos and charged leptons/quarks have a different origin. As a working hypothesis, we assume mass textures which may be generated by the Froggatt-Nielsen mechanism for the charged lepton and quark sectors, which generically leads to strong hierarchies, whereas the neutrino sector is exactly tri-bimaximal with a mild (normal) hierarchy. We find that in this approach, deviations from maximal atmospheric mixing can be introduced without affecting theta(13) and theta(12), whereas a deviation of theta(13) or theta(12) from its tri-bimaximal value will inevitably lead to a similar-sized deviation of the other parameter. Therefore, the already very precise knowledge of theta(12) points towards small sin(2) 2 theta(13) less than or similar to 0.01. The magnitude of this deviation can be controlled by the specific form of the charged lepton texture. (C) 2011 Elsevier B.V. All rights reserved.