Light Sterile Neutrinos: Models and Phenomenology

TL;DR

This paper explores models and phenomenology of eV-scale sterile neutrinos, showing their compatibility with flavor symmetries and impacts on neutrino experiments, including oscillation and double beta decay.

Contribution

It demonstrates how light sterile neutrinos can be incorporated into A_4 flavor symmetry models and proposes an extension of the seesaw mechanism for their natural origin.

Findings

Sterile neutrinos can be accommodated in A_4 models.

Active-sterile mixing perturbs tri-bimaximal mixing.

Sterile neutrinos significantly affect neutrino oscillation observables.

Abstract

Motivated by recent hints in particle physics and cosmology, we study the realization of eV-scale sterile neutrinos within both the seesaw mechanism and flavor symmetry theories. We show that light sterile neutrinos can rather easily be accommodated in the popular A_4 flavor symmetry models. The exact tri-bimaximal mixing pattern is perturbed due to active-sterile mixing, which we discuss in detail for one example. In addition, we find an interesting extension of the type I seesaw, which can provide a natural origin for eV-scale sterile neutrinos as well as visible admixtures between sterile and active neutrinos. We also show that the presence of sterile neutrinos would significantly change the observables in neutrino experiments, specifically the oscillation probabilities in short-baseline experiments and the effective mass in neutrino-less double beta decay. The latter can prove particularly helpful to strengthen the case for eV-scale sterile neutrinos.