Deviation from tri-bimaximal mixings through flavour twisters in inverted and normal hierarchical neutrino mass models

Abstract

We explore a novel possibility for lowering the solar mixing angle (θ 12) from tri-bimaximal mixings, without sacrificing the predictions of maximal atmospheric mixing angle (θ 23 = 45°) and zero reactor angle (θ 13 = 0°) in the inverted and normal hierarchical neutrino mass models having 2–3 symmetry. This can be done through the identification of a flavour twister term in the texture of neutrino mass matrix and the variation of such term leads to lowering of solar mixing angle. For the observed ranges of Δm 221 and Δm 223 , we calculate the predictions on tan2 θ 12 = 0.5, 0.45, 0.35 for different input values of the parameters in the neutrino mass matrix. We also observe a possible transition from inverted hierarchical model having even CP parity (Type-IHA) to inverted hierarchical model having odd CP parity (Type-IHB) in the first two mass eigenvalues, when there is a change in input values of parameters in the same mass matrix. The present work differs from the conventional approaches for the deviations from tri-bimaximal mixing, where the 2–3 symmetry is broken, leading to θ 23 ≠ 45° and θ 13 ≠ 0°.