Testing Neutrino Mass Matrices with Approximate L e − L μ − L τ Symmetry ∗

As neutrino experiments are starting to probe the detailed structure of the neutrino mass matrix, we present sumrules relating its matrix elements for a class of models with approximate Le−Lμ−Lτ symmetry and the observables in neutrino oscillation experiments. We show that regardless of how the above symmetry is broken (whether in the neutrino sector or the charged lepton sector), as long as the breaking terms are small, there is a lower bound on the solar neutrino mixing angle, sin2θ⊙, correlated with the solar mass difference square, ∆m⊙, or the mixing parameter, Ue3. We also discuss models where such patterns can arise.