Quasidegeneracy of Majorana neutrinos and the origin of large leptonic mixing

Abstract

We propose that the observed large leptonic mixing may just reflect a quasidegeneracy of three Majorana neutrinos. The limit of exact degeneracy of Majorana neutrinos is not trivial, as leptonic mixing and even CP violation may occur. We conjecture that the smallness of 1t/131, when compared to the other elements of UPMNS, may be related to the fact that, in the limit of exact mass degeneracy, the leptonic mixing matrix necessarily has a vanishing element. We show that the lifting of the mass degeneracy can lead to the measured value of |C/13| while at the same time accommodating the observed solar and atmospheric mixing angles. In the scenario we consider for the breaking of the mass degeneracy, there is only one CP violating phase, already present in the limit of exact degeneracy, which upon the lifting of the degeneracy generates both Majorana and Dirac-type CP violation in the leptonic sector. We analyze some of the correlations among physical observables and point out that, in most of the cases considered, the implied strength of leptonic Dirac-type CP violation is large enough to be detected in the next round of experiments.

Lepton mixing fromΔ(3n2)andΔ(Hagedorn1, Meroni2, Molinaro3 2015Nuclear Physics B8392050View full textAdd to dashboardCite

“…that has also been found in [33]. For θ 0 in (144) the solar mixing angle takes the value sin 2 θ 12 ≈ 0.318, see also Table 10 in the numerical analysis.…”

Predicting CP violation in deviation from tri-bimaximal mixing of neutrinos

“…In order to answer this question, one should examine the flavor mixing angles and the CP violating Dirac phase strictly. [56][57][58][59][60] In this work, we discuss predictions in the typical four cases of the deviation from the TBM, and propose to test the CP violating Dirac phase at the future experiments, T2K and NOνA. The first two cases are given by the additional rotation of 2-3 or 1-3 generations of neutrinos in the TBM basis, which is called as the tri-maximal mixing.…”

Modulated bimaximal neutrino mixing

“…This indicates either to preclude the BM framework or to harmonize the underlying motivation a little. One such improved follow-up of the BM mechanism is the Bi-Large scenario [37][38][39][40][41]which assumes the solar and the atmospheric angles as equal, non-maximal, and large in general, but leaves a scope to embrace a partial Bi-maximal scenario. Also, in this framework the reactor angle is assumed as large as the Cabibbo angle.…”