Tribimaximal Mixing - Phenomenology

Phenomenology

By virtue of the zero in the tribimaximal mixing matrix, exact tribimaximal mixing would predict zero for all CP-violating asymmetries in the case of Dirac neutrinos (in the case of Majorana neutrinos, Majorana phases are still permitted, and could still lead to CP-violating effects).

For solar neutrinos the large angle MSW effect in tribimaximal mixing accounts for the experimental data, predicting average suppressions in the Sudbury Neutrino Observatory (SNO) and in lower energy solar neutrino experiments (and in long baseline reactor neutrino experiments). The bimaximally mixed in tribimaximal mixing accounts for the factor of two suppression observed for atmospheric muon-neutrinos (and confirmed in long-baseline accelerator experiments). Near-zero appearance in a beam is predicted in exact tribimaximal mixing, and future experiments may well rule this out. Further characteristic predictions of tribimaximal mixing, e.g. for very long baseline and (vacuum) survival probabilities, will be extremely hard to test experimentally.

The L/E flatness of the electron-like event ratio at Super-Kamiokande severely restricts the neutrino mixing matrices to the form:

Additional experimental data fixes . The extension of this result to the CP violating case is found in.