How a non-hierarchical neutrino mass matrix can arise

How a Non-hierarchical Neutrino Mass Matrix Can Arise

One puzzle of neutrino masses and mixings is that they do not exhibit the kind of strong “hierarchy” that is found for the quarks and charged leptons. Neutrino mass ratios and mixing angles are not small. A possible reason for this is proposed here. It is based on the fact that typical realistic grand unified models contain particles with unification-scale masses which, when integrated out, can...

Toward a Neutrino Mass Matrix

left-handed (two-component) neutrinos νe, νμ, and ντ with the left-handed fields se, sμ, and sτ that are the charge conjugates of the right-handed neutrino fields νre, νrμ, νrτ , i.e., se = −iσ2 ν∗ re = (ν† re2,−ν re1), etc. The six left-handed neutrino fields form a six-vector, N = (νe, νμ, ντ , se, sμ, sτ ). The only mass term available for two left-handed neutrino fields Ni and Nj isMij (Ni1...

Tripartite Neutrino Mass Matrix

The 3 × 3 Majorana neutrino mass matrix is written as a sum of 3 terms, i.e. Mν = MA +MB +MC , where MA is proportional to the identity matrix and MB,C are invariant under different Z3 transformations. This Mν is very suitable for understanding atmospheric and solar neutrino oscillations, with sin 2θatm and tan 2 θsol fixed at 1 and 0.5 respectively, in excellent agreement with present data. It...

Natural Neutrino Mass Matrix

Naturalness of the neutrino mass hierarchy and mixing is studied. First we select among 12 neutrino mixing patterns a few patterns, which could form the natural neutrino mass matrix. Further we show that if the Dirac neutrino mass matrix is taken as the natural one in the quark sector, then only two mixing patterns without the large mixing lead to the natural right-handed Majorana mass matrix. ...

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