On deviations from bimaximal neutrino mixing

By Paul H. Frampton, S. Petcov, W. Rodejohann. 2004

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Abstract The PMNS neutrino mixing matrix U PMNS is in general a product of two unitary matrices U lep and U ν arising from the diagonalization of the charged lepton and neutrino mass matrices, U PMNS =U † lep U ν . Assuming that U ν is a bimaximal mixing matrix, we investigate the possible forms of U lep . We identify three possible generic structures of U lep , which are compatible with the existing data on neutrino mixing. One corresponds to a hierarchical “CKM-like” matrix. In this case relatively large values of the solar neutrino mixing angle θ sol , and of | U e 3 | 2 ≡|( U PMNS ) e 3 | 2 , are typically predicted, tan 2 θ sol ≳0.42, | U e 3 | 2 ≳0.02, while the atmospheric neutrino mixing angle θ atm can deviate noticeably from π /4, sin 2 2 θ atm ≳0.95. The second corresponds to one of the mixing angles in U lep being equal to π /2, and predicts practically maximal atmospheric neutrino mixing sin 2 2 θ atm ≃1. Large atmospheric neutrino mixing, sin 2 2 θ atm ≳0.95, is naturally predicted by the third possible generic structure of U lep , which corresponds to all three mixing angles in U lep being large. We focus especially on the case of CP-non-conservation, analyzing it in detail. We show how the CP-violating phases, arising from the diagonalization of the neutrino and charged lepton mass matrices, contribute to the measured neutrino mixing observables.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/d22c8e6612d4353f04f5351cf7861bed1ee9f4f4

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