Relating small neutrino masses and mixing

Abstract

Experiments on neutrino oscillations have uncovered several small parameters, θ13 being a prominent one. Others are the solar mass splitting vis-à-vis the atmospheric one and the deviation of θ23 from maximal mixing. In this talk, (talk given at the International Conference on Massive Neutrinos, Singapore, 9–13 February 2015) we elaborate on a neutrino mass model based on the see-saw mechanism in which the mixing angles to start with are either vanishing (θ13 and θ12) or π/4 (θ23). The atmospheric mass splitting is taken as a part of this initial structure but the solar splitting is absent. A perturbative contribution, originating from a Type-I see-saw, results in nonzero values of θ13, θ12, [Formula: see text], and shifts θ23 slightly from π/4, interrelating them all. The model incorporates CP-violation, the phase δ being close to 3π/2 for (a) quasidegeneracy or (b) inverted mass ordering. It will be put to test as the neutrino parameters get better determined.