Sterile Neutrinos

TL;DR

This paper discusses the necessity of sterile neutrinos to explain various neutrino oscillation experiments and proposes a parity doubling model to account for their lightness and properties.

Contribution

It introduces a parity doubling scenario of the Standard Model to explain the lightness and nature of sterile neutrinos, linking them to a mirror sector.

Findings

Sterile neutrinos can explain LSND, solar, and atmospheric neutrino data.

A parity doubling model provides a theoretical basis for their lightness.

Possible experimental tests of the mirror sector hypothesis are discussed.

Abstract

A simultaneous understanding of the results of the LSND experiment indicating $\nu_{\mu}-\nu_e$ oscillation together with other evidences for neutrino oscillations from solar and atmospheric neutrino data seems to require the existence of at least one sterile neutrino. One can also give other plausible astrophysical arguments that seem to require light sterile neutrinos. A major theoretical challenge posed by their existence is to understand why they are so light. A scenario is presented where one assumes a parity doubling of the standard model with identical matter and gauge content. The neutrinos of the parity doubled (mirror) sector are light for the same reason that the known neutrinos are light and since they do not couple to the known W and Z bosons, they can be identified with the sterile neutrinos. Some of the implications and possible tests of this hypothesis are mentioned.