Neutrino mass ordering and μ-τ reflection symmetry breaking**Supported by National Natural Science Foundation of China (11135009, 11375207)

Abstract

If the neutrino mass spectrum turns out to be m3<m1<m2, it may be relabeled as such that all the masses of fundamental fermions with the same electrical charges are in order. In this case the columns of the 3×3 lepton flavor mixing matrix U should be reordered accordingly, and the resulting pattern U′ may involve one or two large mixing angles in the standard parametrization or its variations. Since the Majorana neutrino mass matrix remains unchanged in such a mass relabeling, a possible μ-τ reflection symmetry is respected in this connection and its breaking effects are model-independently constrained at the 3σ level by using current experimental data.