Democratic-type neutrino mass matrix

Abstract

We consider the democratic-type neutrino mass matrix and show that this matrix predicts the atmospheric neutrino mixing to be almost maximal, ${\sin }^{2}2{\theta }_{atm}>0.999$ as well as the large CP violation (the CP violation phase in the standard form is maximal $\delta =\pi /2$). We construct the $Z_3$ symmetric dimension five effective Lagrangian with two up-type Higgs doublets and show that this Lagrangian leads to the democratic neutrino mass matrix. Furthermore, we consider the restricted model with one up-type Higgs doublet and obtain the prediction, $0.87<{\sin }^{2}2{\theta }_{sol}<8/9$.

LaTeX, 7 pages; Talk given at Workshop on Neutrino Oscillations and their Origin, Fuji-Yoshida, Japan, 11-13 Feb 2000