Relating large $U_{e3}$ to the ratio of neutrino mass-squared differences

Abstract

The non-zero and sizable value of $U_{e3}$ puts pressure on flavor symmetry models which predict an initially vanishing value. Hence, the tradition of relating fermion mixing matrix elements with fermion mass ratios might need to be resurrected. We note that the recently observed non-vanishing value of $U_{e3}$ can be related numerically to the ratio of solar and atmospheric mass-squared differences. The most straightforward realization of this can be achieved with a combination of texture zeros and a vanishing neutrino mass. We analyze the implications of some of these possibilities and construct explicit flavor symmetry models that predict these features.