Mrinal Kumar Das, Debasish Borah, Rinku Mishra
We present an analysis of normal and inverted hierarchical neutrino mass models within the framework of tri-bi-maximal (TBM) mixing. Considering the neutrinos to be quasi-degenerate (QDN), we study two different neutrino mass modes with mass eigenvalues $(m_1, -m_2, m_3)$ and $(m_1, m_2, m_3)$ for both normal hierarchical (NH) and inverted hierarchical (IH) cases. Incorporating the type II seesaw contribution to tiny neutrino masses with that of type I, we compare the predictions for neutrino mass parameters with the experimental values. Assuming the Dirac neutrino mass matrix to be diagonal and the right handed Majorana mass matrix to be of general form, we consider both charged lepton (CL) type as well as up quark (UQ) type Dirac neutrino mass matrices. Within such a framework and incorporating both oscillation as well as cosmology data, we show that QDN scenario of neutrino masses can still survive in nature with some minor exceptions. A viable extension of the standard model with an abelian gauged flavor symmetry is briefly discussed which can give rise to the desired structure of the Dirac and Majorana mass matrices.
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http://arxiv.org/abs/1209.0280
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