We have shown that non-zero U e3 is generated in a see-saw type softly broken A 4 symmetric model through a single parameter perturbation in m D in a single element. We have explored all possible 9 cases to study the neutrino mixing angles considering the best fitted values of ∆m 2 and ∆m 2 atm with all parameters real. We have extended our analysis for the complex case and demonstrated large low energy CP violation (J CP 10 −2 ) and m ee in addition to mixing and mass pattern. We have also investigated leptogenesis and for a reasonable choice of model parameters compatible with low energy data, WMAP value of baryon asymmetry 6 × 10 −10 is obtained for right handed neutrino mass scale M 0 10 13 GeV. We have obtained a relation among the phases responsible for leptogenesis and have shown that those phases also have correlations with low energy CP violating phases.
Cyclic symmetry in the neutrino sector with the type-I seesaw mechanism in the mass basis of charged leptons and right chiral neutrinos (N iR , i = e, µ, τ ) generates two fold degenerate light neutrino and three fold degenerate heavy neutrino mass spectrum. Consequently, such scheme, produces vanishing one light neutrino mass squared difference and lepton asymmetry. To circumvent such unphysical outcome, we break cyclic symmetry in the diagonal right chiral neutrino mass term by a small breaking parameter. Nonzero mass squared differences and mixing angles are generated with the help of the small breaking parameter. Smallness of the breaking parameter opens up a possibility of resonant leptogenesis. Assuming complex Yukawa couplings, we derive generalized expressions flavor dependent CP asymmetry parameters (ε α i ) which are valid for quasi degenerate as well as hierarchical mass spectrum of right handed neutrinos. There after we set up the chain of coupled Boltzmann equations (which are flavor dependent too) which have to be solved in order to get the final lepton asymmetries. Depending upon the temperature regime the CP asymmetries and the Boltzmann equations may also be flavor independent. As our goal is to study the enhancement of CP asymmetry due to quasi degeneracy of right handed neutrinos, we select only the lowest allowed (by neutrino oscillation data) value of breaking parameter (and other corresponding Lagrangian parameters) and estimate the baryon asymmetry parameter Y B . Experimental constraint of Y B introduces a bound on right handed neutrino mass which remained unrestricted by neutrino oscillation data. *
We investigate 'Scaling ansatz' in the neutrino sector within the framework of type I seesaw mechanism with diagonal charged lepton and right handed Majorana neutrino mass matrices (M R ).We also assume four zero texture of Dirac neutrino mass matrices (m D ) which severely constrain the phenomenological outcomes of such scheme. Scaling ansatz and the present neutrino data allow only Six such matrices out of 126 four zero Yukawa matrices. In this scheme, in order to generate large θ 13 we break scaling ansatz in m D through a perturbation parameter and we also show our breaking scheme is radiatively stable. We further investigate CP violation and baryogenesis via leptogenesis in those surviving textures.
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