New type of complex neutrino mass texture and μ-τ symmetry

Relying upon the usefulness of the μ-τ symmetry, we find a new type of neutrino mass texture with a single phase parameter δ that describes maximal atmospheric neutrino mixing and Dirac CP violation due to the presence of δ. The Majorana phase associated with the third massive neutrino turns out to be identical to the Dirac phase while other Majorana phases vanish. The nonvanishing reactor neutrino mixing angle θ13 is induced by a μ-τ symmetry breaking effect. Flavor neutrino masses that supply the μ-τ symmetry breaking terms become pure imaginary for δ=±π/2, leading to maximal CP violation. There is a parameter denoted by η, which is either O(√(Δm·2/Δmatm2)) in the normal mass hierarchy, or O(Δm·2/Δmatm2) in the inverted mass hierarchy. In the inverted mass hierarchy, the contribution of O(sin2θ13) is found to be significant and cannot be neglected. Our texture also leads to quasidegenerate neutrinos with masses of O(√(Δmatm2)), which serves as the scale for the effective neutrino mass in (ββ)0ν decay. This texture does not include η, and Δm·2 naturally arises from contributions of O(sin2θ13) to give Δm·2/Δmatm2∼sin2θ13, yielding the prediction of sin2θ13=O(10-2)