Large|U_e3|and tribimaximal mixing

Abstract

We investigate in a model-independent way to what extent one can perturb tribimaximal mixing in order to generate a sizable value of |U_e3|, while at the same time keeping solar neutrino mixing near its measured value, which is close to sin ²θ₁₂ = ¹₃. Three straightforward breaking mechanisms to generate |U_e3≃ 0.1 are considered. For charged lepton corrections, the suppression of a sizable contribution to sin ²θ₁₂ can be achieved if CP violation in neutrino oscillations is almost maximal. Generation of the indicated value of |Ue3|≃0.1 through renormalization group corrections requires the neutrinos to be quasidegenerate in mass. The consistency with the allowed range of sin ²θ₁₂ together with large running of |U_e3| forces one of the Majorana phases to be close to π. This implies large cancellations in the effective Majorana mass governing neutrinoless double beta ((ββ)_0ν) decay, constraining it to lie near its minimum allowed value of m₀cos ²θ₁₂, where m₀ ≳ 0.1  eV. Finally, explicit breaking of the neutrino mass matrix in the inverted hierarchical and quasidegenerate neutrino mass spectrum cases is similarly correlated with the (ββ)_0ν-decay effective Majorana mass, although to a lesser extent. The implied values for the atmospheric neutrino mixing angle θ₂₃ are given in all cases.