Heavy right-handed neutrino dark matter in left-right models

TL;DR

This paper proposes a non-supersymmetric left-right model where the lightest right-handed neutrino serves as thermal dark matter, with mass bounds from relic density and potential to explain IceCube PeV neutrinos.

Contribution

It introduces a novel left-right extension with a stable right-handed neutrino dark matter candidate and explores its mass bounds and decay properties.

Findings

Lower bound on RHN DM mass around TeV from relic density

Unitarity upper bound on RHN DM mass in the multi-TeV to PeV range

RHN DM can be long-lived and explain IceCube PeV neutrinos

Abstract

We show that in a class of non-supersymmetric left-right extensions of the Standard Model (SM), the lightest right-handed neutrino (RHN) can play the role of thermal Dark Matter (DM) in the Universe for a wide mass range from TeV to PeV. Our model is based on the gauge group $SU(3)_c \times SU(2)_L\times SU(2)_R\times U(1)_{Y_L}\times U(1)_{Y_R}$ in which a heavy copy of the SM fermions are introduced and the stability of the RHN DM is guaranteed by an automatic $Z_2$ symmetry present in the leptonic sector. In such models the active neutrino masses are obtained via the type-II seesaw mechanism. We find a lower bound on the RHN DM mass of order TeV from relic density constraints, as well as an unitarity upper bound in the multi-TeV to PeV scale, depending on the entropy dilution factor. The RHN DM could be made long-lived by soft-breaking of the $Z_2$ symmetry and provides a concrete example of decaying DM interpretation of the PeV neutrinos observed at IceCube.