Heavy neutrinos in particle physics and cosmology

TL;DR

This paper reviews the role of heavy right-handed neutrinos in particle physics and cosmology, highlighting their potential to explain neutrino oscillations, baryon asymmetry, dark matter, and dark radiation, with a focus on experimental prospects.

Contribution

It provides a comprehensive review of the phenomenology of heavy right-handed neutrinos across different mass scales, especially at least a keV, and discusses experimental discovery opportunities.

Findings

Heavy neutrinos could explain neutrino oscillations and cosmological phenomena.

Low scale leptogenesis via heavy neutrinos is testable in upcoming experiments.

Experimental searches for heavy neutrinos are promising in the near future.

Abstract

Neutrinos are the only particles in the Standard Model of particle physics that have only been observed with left handed chirality to date. If right handed neutrinos exist, they would not only explain the observed neutrino oscillations, but could also be responsible for several phenomena in cosmology, including the baryon asymmetry of the universe, dark matter and dark radiation. A crucial parameter in this context is their Majorana mass, which in principle could lie anywhere between the eV scale and GUT scale. The implications for experiments and cosmology strongly depend on the choice of the mass scale. We review recent progress in the phenomenology of right handed neutrinos with different masses, focusing on scenarios in which the mass is at least a keV. We emphasise the possibility to discover heavy neutrinos that are responsible for the baryon asymmetry of the universe via low scale leptogenesis in near future experiments, such as LHC, BELLE II, SHiP, FCC-ee or CEPC.