A model-independent investigation on quasi-degenerate neutrino mass models and their significance

The prediction of possible hierarchy of neutrino masses mostly depends on the model chosen. Dissociating the μ-τ interchange symmetry from discrete flavor symmetry based models, makes the neutrino mass matrix less predictive and motivates one to seek the answer from different phenomenological frameworks. This insists on proper parametrization of the neutrino mass matrices concerning individual hierarchies. In this work, an attempt has been made to study the six different cases of quasi-degenerate (QDN) neutrino models with mass matrices, mLLν parametrized with two free parameters (α,η), standard Wolfenstein parameter (λ) and input mass scale, m0∼0.08eV. We start with a μ-τ symmetric neutrino mass matrix followed by a correction from charged lepton sector. The parametrization emphasizes on the existence of four independent texture zero building blocks common to all the QDN models under μ-τ symmetric framework and is found to be invariant under any choice of solar angle. In our parametrization, solar angle is controlled from neutrino sector whereas the charged lepton sector drives the reactor and atmospheric mixing angles. The individual models are tested in the framework of oscillation experiments, cosmological observation and future experiments involving β-decay and 0νββ experiments, and any reason to discard the QDN mass models with relatively lower mass is unfounded. Although the QDNH-Type IA model shows strong preference for sin2θ12=0.32, yet this is not sufficient to rule out the other models. The present work leaves a scope to extend the search of most favorable QDN mass model from observed baryon asymmetry of the Universe.