EV-scale sterile neutrinos from an extra dimension

Nobuchika Okada,Shinsuke Kawai

doi:10.1103/physrevd.100.115043

Abstract

Motivated by the short-baseline neutrino oscillation anomalies that suggest the existence of sterile neutrinos at the eV scale, we construct a scenario of a seesaw mechanism for 3+1 light neutrinos implemented by warped compactification of an extra dimension. As the seesaw mechanism necessitates at least two right-handed neutrinos at mass scales much larger than eV, incorporating an eV-scale sterile neutrino into a seesaw entails large mass hierarchies among the singlet neutrinos. We show that such hierarchies can be naturally explained by moderate fluctuations of the five-dimensional fermion mass parameters.

Highlights

The progress of neutrino physics is remarkable
Consistency with other experiments is still a matter of debate, if neutrino oscillations are to be responsible for the anomalies,1 the combined Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE results strongly signal the existence of sterile neutrinos around the mass scale of eV
The discovery of sterile neutrinos would have a huge impact on particle physics and cosmology, not merely on the physics of neutrinos

Summary

INTRODUCTION

The progress of neutrino physics is remarkable. Today, precise measurements of the neutrino mass-squared differences and the mixing angles are becoming available [1]. A theoretical challenge would to work out how the eV-scale sterile neutrinos may be incorporated in a sensible theory beyond the Standard Model (SM). Since these leptons are SM gauge singlets, and as the seesaw mechanism is one of the leading candidates for the generation. It is well known that the Uð1ÞB−L-extended Standard Model, which is obtained by gauging the global Uð1ÞB−L symmetry of the SM and gives rise to the type I seesaw when the Uð1ÞB−L symmetry is spontaneously broken, is anomaly-free only if there are three right-handed neutrinos. The minimal anomaly-free model must have one light (eV-scale) and two heavy (seesaw-scale) right-handed neutrinos, embedded in the Uð1ÞB−L-extended Standard Model. We propose a simple compactification scenario that gives rise to a naturally tuned desired neutrino mass matrix (3)

THE MODEL

Singlet neutrinos from bulk fermions

Majorana masses

Dirac masses

BENCHMARK FOR THE SEESAW MECHANISM

FINAL REMARKS