Riddle of the Neutrino Mass

TL;DR

This paper reviews current theories and ideas on the origin and nature of neutrino mass, exploring connections to charged fermions, mixing, and potential new physics at various energy scales, including sterile neutrinos.

Contribution

It presents new ideas and synthesizes existing approaches on neutrino mass origins, emphasizing the role of sterile neutrinos and the importance of CP phase and mass hierarchy measurements.

Findings

Data suggest two different new physics mechanisms behind neutrino mass.

Determination of CP phase and mass hierarchy is crucial for understanding neutrino physics.

Sterile neutrinos may be key to resolving the neutrino mass riddle.

Abstract

We discuss some known approaches and results as well as few new ideas concerning origins and nature of neutrino mass. The key issues include (i) connections of neutrino and charged fermions masses, relation between masses and mixing, energy scale of new physics behind neutrino mass where possibilities spread from the Planck and GUT masses down to a sub-eV scale. The data hint two different new physics involved in generation of neutrino mass. Determination of the CP phase as well as mass hierarchy can play important role in identification of new physics. It may happen that sterile neutrinos provide the key to resolve the riddle.