Deviations from tri-bimaximal neutrino mixing using type II seesaw

Abstract

We study the possibility of generating deviations from tri-bimaximal (TBM) neutrino mixing to explain the non-zero reactor mixing angle within the framework of both type I and type II seesaw mechanisms. The type I seesaw term gives rise to the μ–τ symmetric TBM pattern of neutrino mass matrix as predicted by generic flavor symmetry models like A4 whereas the type II seesaw term gives rise to the required deviations from TBM pattern to explain the non-zero θ13. Considering extremal values of Majorana CP phases such that the neutrino mass eigenvalues have the structure (m1,−m2,m3) and (m1,m2,m3), we numerically fit the type I seesaw term by taking oscillation as well as cosmology data and then compute the predictions for neutrino parameters after the type II seesaw term is introduced. We consider a minimal structure of the type II seesaw term and check whether the predictions for neutrino parameters lie in the 3σ range. We also outline two possible flavor symmetry models to justify the minimal structure of the type II seesaw term considered in the analysis.