Phased breaking of μ-τ Symmetry and leptogenesis

Nonvanishing Ue3 has been theoretically related to a certain flavor symmetry breaking in the neutrino sector. We propose a scenario to break the μ-τ symmetry so as to accommodate the nonvanishing Ue3. Our scenario is constructed in the context of a seesaw model, and the μ-τ symmetry breaking is achieved by introducing a CP phase in the Dirac Yukawa matrix. We also show how the deviation of θ23 from the maximal mixing and nonvanishing Ue3 depend on the CP phase. Neutrino mixings and the neutrino mass-squared differences are discussed, and the amplitude in neutrinoless double beta decay mee are also predicted. We found that a tiny breaking of the μ-τ symmetry due to mass splitting between two degenerate heavy Majorana neutrinos on top of the Dirac CP phase can lead to successful leptogenesis. We examine how leptogenesis can be related with low energy neutrino measurement, and show that our predictions for Ue3 and mee can be constrained by the current observation of baryon asymmetry.