Massive and massless neutrinos on unbalanced seesawsSupported by National Natural Science Foundation of China (10425522)
Xing Zhi-Zhong
Журнал:
Chinese Physics C
Дата:
2008-02-01
Аннотация:
The observation of neutrino oscillations requires new physics beyond the standard model (SM). A SM-like gauge theory with p lepton families can be extended by introducing q heavy right-handed Majorana neutrinos but preserving its SU(2)<sub>L</sub>×U(1)<sub>Y</sub> gauge symmetry. The overall neutrino mass matrix M turns out to be a symmetric (p+q)×(p+q) matrix. Given p>q, the rank of M is in general equal to 2q, corresponding to 2q non-zero mass eigenvalues. The existence of (p-q) massless left-handed Majorana neutrinos is an exact consequence of the model, independent of the usual approximation made in deriving the Type-I seesaw relation between the effective p×p light Majorana neutrino mass matrix M<sub>ν</sub> and the q×q heavy Majorana neutrino mass matrix M<sub>R</sub>. In other words, the numbers of massive left- and right-handed neutrinos are fairly matched. A good example to illustrate this ``seesaw fair play rule'' is the minimal seesaw model with p=3 and q=2, in which one massless neutrino sits on the unbalanced seesaw.
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