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Register a new userValidity of quasi-degenerate neutrino mass models and their predictions on baryogenesis
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Quasi-degenerate neutrino mass models (QDN) which can explain the current data on neutrino masses and mixings,are studied. In the first part, we study the effect of CP-phases on QDN mass matrix obeying $mu-tau$ symmetry in normal hierarchical (QD-NH) and inverted hierarchical (QD-IH) patterns.The numerical predictions are consistent with observed data on solar mixing angle, absolute neutrino mass parameter consistent with neutrinoless double beta decay mass parameter and sum of three absolute neutrino masses from cosmological bound.The neutrino mass matrix is parameterized using only two unknown parameters. The second part deals with the estimation of observed baryon asymmetry of the universe. The prediction is nearly consistent with observation with flavoured thermal leptogenesis scenario. QD-NH model appears to be more favourable than those of QD-IH models.The present analysis shows that the three absolute neutrino masses may exhibit quasi-degenerate pattern in nature. They are far from discrimination at the moment.
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A parametrisation of the degenerate neutrino mass matrix obeying $mu -tau$ symmetry, is introduced for detailed numerical analysis. As a continuation of our earlier work on normal and inverted hierarchical models, the present parametrisation for degenerate models has the ability to lower the solar mixing angle below the tri-bimaximal value $tan^{2}theta_{12}=0.5$, while maintaining the condition of maximal atmospheric mixing angle and zero reactor angle. The combined data on the mass-squared differences derived from various oscillation experiments, and also from the bounds on absolute neutrino masses in $0 ubetabeta$ decay and cosmology, gives certain constraints on the validity of the degenerate models.
We study finite quantum corrections for several well known neutrino mixing matrices and find that it is hard to account for the large value of theta_13 recently reported by T2K and MINOS. To nicely reproduce all experimentally favored neutrino mixing angles and masses, we propose a new neutrino mixing pattern. We also demonstrate a simple realization by slightly extending the standard model to illustrate the quantum corrections.
We investigate an interesting correlation among dark matter phenomenology, neutrino mass generation and GUT baryogenesis, based on the scotogenic model. The model contains additional right-handed neutrinos $N$ and a second Higgs doublet $Phi$, both of which are odd under an imposed $Z_2$ symmetry. The neutral component of $Phi$, i.e. the lightest of the $Z_2$-odd particles, is the dark matter candidate. Due to a Yukawa coupling involving $Phi$, $N$ and the Standard Model leptons, the lepton asymmetry is converted into the dark matter asymmetry so that a non-vanishing $B-L$ asymmetry can arise from $(B-L)$-conserving GUT baryogenesis, leading to a nonzero baryon asymmetry after the sphalerons decouple. On the other hand, $Phi$ can also generate neutrino masses radiatively. In other words, the existence of $Phi$ as the dark matter candidate resuscitates GUT baryogenesis and realizes neutrino masses.
The effects of CP-phases on the three absolute quasi-degenerate Majorana neutrino (QDN) masses are stud-ied with neutrino mass matrices obeying {mu} - {tau} symmetry for normal as well as inverted hierarchical mass patterns. We have made further investigations on 1) the prediction of solar mixing angle which lies below tri-bimaximal mixing value in consistent with neutrino oscillation observational data, 2) the prediction on absolute neutrino mass parameter (mee) in 0{ u}{beta}{beta} decay, and 3) cosmological bound on the sum of the three absolute neutrino masses. The numerical analysis is carried out through the parameterization of neu- trino mass matrices using only two unknown parameters ({epsilon}, {eta}) within {mu} - {tau} symmetry. The results show the validity of QDN mass models in both normal and inverted hierarchical patterns. These models are far from discrimination and hence not yet ruled out. The results presented in this article are new and have subtle ef- fects in the discrimination of neutrino mass models.
In this short review, we see some typical models in which light neutrino masses are generated at the loop level. These models involve new Higgs bosons whose Yukawa interactions with leptons are constrained by the neutrino oscillation data. Predictions about flavor structures of $ell to overline{ell}_1 ell_2 ell_3$ and leptonic decays of new Higgs bosons via the constrained Yukawa interactions are briefly summarized in order to utilize such Higgs as a probe of $ u$ physics.
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