Generalized tri-bimaximal neutrino mixing and its sensitivity to radiative corrections

We argue that the tri-bimaximal neutrino mixing pattern V0 or its generalized form V0′, which includes two arbitrary Majorana phases of CP violation, may result from an underlying flavor symmetry at a superhigh energy scale close to the seesaw scale (∼1014GeV). Taking the working assumption that three neutrino masses are nearly degenerate, we calculate radiative corrections to V0 and V0′ in their evolution down to the electroweak scale (∼102GeV). Three mixing angles of V0 or V0′ are essentially stable against radiative corrections in the standard model (SM). In the minimal supersymmetric standard model (MSSM), however, V0 is in general disfavored and V0′ can be compatible with current neutrino oscillation data if its two Majorana phases α1 and α2 are properly fine-tuned. We also find that it is possible to radiatively generate the CP-violating phase δ from α1 and α2, and δ may keep on staying at its quasi-fixed point in either the SM or the MSSM.