$θ_{13}$, $μτ$ symmetry breaking and neutrino Yukawa textures

Abstract

Within the type-I seesaw and in the basis where charged lepton and heavy neutrino mass matrices are real and diagonal, $μτ$ symmetric four and three zero neutrino Yukawa textures are perturbed by lowest order $μτ$ symmetry breaking terms. These perturbations are taken to be the {\it most general ones for those textures}. For quite small values of those symmetry breaking parameters, permitting a lowest order analysis, current best-fit ranges of neutrino mass squared differences and mixing angles are shown to be accommodable, including a value of $θ_{13}$ in the observed range, provided all the light neutrinos have an inverted mass ordering.

20 pages, 8 figures, published version with considerable elaboration