Brokenμ−τsymmetry and leptonicCPviolation

Abstract

We propose that leptonic CP violation arises from a breaking of the {mu}-{tau} exchange symmetry in the neutrino mass matrix which in turn is indicated by the near maximal atmospheric neutrino mixing and the near zero {theta}{sub 13}. We find that for the case of a normal hierarchy, present data already restrict the way CP violation may appear in the neutrino mass matrix and there is an interesting correlation between the mixing angle {theta}{sub 13}, the solar mixing angle {theta}{sub 12} and the Dirac CP phase. In the inverted hierarchy only {theta}{sub 13} and the Dirac phase are linked. We also discuss the impact of this kind of CP violation on the deviation of the atmospheric mixing from its maximal value. Moreover, if corrections to {mu}-{tau} symmetry arise from the charged lepton sector, where {mu}-{tau} symmetry is known to be broken anyway, we find interesting connections between the CP-even and CP-odd terms as well. Our predictions are testable in the proposed long baseline neutrino experiments.