Is it all in a perturbation?

Abstract

Starting from an unperturbed scenario devoid of both solar splitting and θ13, characterized only by the observed atmospheric splitting and maximal mixing in this sector, we devise a single perturbation arising out of a Type I Seesaw Mechanism that can generate non-zero θ13, Δm2solar, θ12 together with deviations of θ23 from π/4 (in both the octants), all consistent with the recent measurements. Although a real perturbation shows preference towards normal ordering, both the mass ordering options are permitted by the complex case. CP phase δ ∼ π/2, 3π/2 was found in case of inverted ordering as well as in the quasidegenerate regime.