Quantum Effects for the Neutrino Mixing Matrix in a Democratic-Type Model

We investigate the quantum effects for the democratic-type neutrino massmatrix given at the right-handed neutrino mass scale $m_R$ in order to see (i)whether $\theta_{23}=-\pi/4$ predicted by the model is stable to explain theatmospheric neutrino anomaly, (ii) how $\theta_{12}$ and $\theta_{13}$ behave,and (iii) whether the predicted Dirac CP phase $\delta$ keeps maximal size, atthe weak scale $m_Z$. We find that, for the (inversely) hierarchical massspectrum with $m_1\sim m_2$, $\theta_{23}$ and $\theta_{13}$ are stable, while$\theta_{12}$ is not so, which leads to the possibility that the solar neutrinomixing angle can become large at $m_Z$ even if it is taken small at $m_R$. Wealso show that $\delta$ keeps almost maximal for the above mass spectrum, andour model can give the large CP violation effect in the future neutrinooscillation experiments if the solar neutrino puzzle is explained by the largemixing angle MSW solution.Comment: LaTeX, 21 pages, 2 figures, some mistakes correcte