Neutrino Mass Matrix with Broken Scaling in Light of LMA and Dark-LMA Solutions

Abstract

In the present work we have investigated patterns of broken “scaling” ansatz of the neutrino mass matrix. The scaling neutrino mass matrix is disallowed by the current neutrino oscillation data as it predicts vanishing reactor angle (\(\theta _{13}=0\)). Also, any prospective extension of the Standard Model that accommodates small neutrino masses may inherently entail non-standard interactions (NSIs) between neutrinos and matter giving rise to an alternative parameter space (Dark-LMA) that remains compatible with existing neutrino oscillation data. We study possible breaking scenarios of scaling ansatz in light of the large mixing angle (LMA) and Dark-LMA solutions suggested by current neutrino oscillation data. The normal hierarchical neutrino mass spectrum is ruled out in all three possible breaking patterns. One of the interesting feature of these breaking scenarios is the interplay between \(\theta _{23}\)-octant and possible CP violation. We find that the model allows maximal CP violation for \(\theta _{23}\) above \(6\%\) of its maximal value which, interestingly, is close to its current best-fit value for inverted hierarchical neutrino masses. We have, also, investigated the implications for effective Majorana neutrino mass parameter \(|M_{ee}|\) for allowed breaking patterns. The correlation behavior of Majorana CP phases, which can be probed in \(0\nu \beta \beta \) decay experiments, is found to have the capability of distinguishing LMA and Dark-LMA solutions.