Neutrino Mixing and CP Phase Correlations

A special form of the $3\times 3$ Majorana neutrino mass matrix derivable from $\mu -\tau$ interchange symmetry accompanied by a generalized $CP$ transformation was obtained many years ago. It predicts ${\theta }_{23}=\pi \mathrm{/}4$ as well as ${\delta }_{CP}=\pm \pi \mathrm{/}2$, with ${\theta }_{13}\mathrm{\ne }0$. Whereas this is consistent with present data, we explore a deviation of this result which occurs naturally in a recent proposed model of radiative inverse seesaw neutrino mass.