Symmetry based parameterizations of the lepton mixing matrix

Abstract

There are many mixing schemes based upon flavor symmetries that predict a vanishing $\theta_{13}$. These mixing schemes need corrections or modifications to account for recent experimental measurements of non-zero $\theta_{13}$. We propose new parameterizations for the lepton mixing matrix to quantify the minimal modifications needed in these mixing schemes. The parameterizations can be factorized in two parts: $U_{0}(a,b)$ and $R(\theta,\phi)$. The first factor can be viewed as a zeroth order mixing matrix coming from some flavor symmetry. It reproduces the popular mixing schemes based upon flavor symmetries for suitable values of $a$ and $b$. The second factor can be interpreted as a minimal modification to the mixing matrix and is responsible for non zero $\theta_{13}$, non-maximal $\theta_{23}$ and CP violation. We also find the experimentally allowed parameter space for the parameters $a$ and $b$ and compare it with the symmetry based values for these parameters.