Large U_{e3} and Tri-bimaximal Mixing

Understand

We investigate in a model-independent way to what extent one can perturb tri-bimaximal 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^2 theta_{12} = 1/3.

• Three straightforward breaking mechanisms to generate |U_{e3}| of about 0.1 are considered.
• For charged lepton corrections, the suppression of a sizable contribution to sin^2 theta_{12} can be achieved if CP violation in neutrino oscillations is almost maximal.
• Generation of the indicated value of |U_{e3}| of about 0.1 through renormalization group corrections requires the neutrinos to be quasi-degenerate in mass.