Phenomenological implications of the Friedberg-Lee transformation in a neutrino mass model with $μτ$-flavored CP symmetry

Abstract

We propose a neutrino mass model with $μτ$-flavored CP symmetry, where the effective light neutrino Lagrangian enjoys an additional invariance under a Friedberg-Lee (FL) transformation on the left-handed flavor neutrino fields, that leads to a highly predictive and testable scenario. While both types of the light neutrino mass ordering, i.e., Normal Ordering (NO) as well as the Inverted Ordering (IO) are allowed, the absolute scale of neutrino masses is fixed by the vanishing determinant of light Majorana neutrino mass matrix $M_ν$. We show that for both types of mass ordering, whilst the atmospheric mixing angle $θ_{23}$ is in general nonmaximal ($θ_{23}\neq π/4$), the Dirac CP phase $δ$ is exactly maximal ($δ=π/2,3π/2$) for IO and nearly maximal for NO owing to $\cosδ\propto \sinθ_{13}$. For the NO, very tiny nonvanishing Majorana CP violation might appear through one of the Majorana phases $β$; otherwise the model predicts vanishing Majorana CP violation. Thus, despite the fact, that from the measurement of $θ_{23}$, it is difficult to rule out the model, any large deviation of $δ$ from its maximality, will surely falsify the scenario. For a comprehensive numerical analysis, beside fitting the neutrino oscillation global fit data, we also present a study on the $ν_μ\rightarrow ν_e$ oscillation which is expected to show up Dirac CP violation in different long baseline experiments. Finally, assuming purely astrophysical sources, we calculate the Ultra High Energy (UHE) neutrino flavor flux ratios at neutrino telescopes, such as IceCube, from which statements on the octant of $θ_{23}$ could be made in our model.