Cosmological bounds of sterile neutrinos in a $SU(3)_C\otimes SU(3)_L\otimes SU(3)_R\otimes U(1)_N$ model as dark matter candidates

TL;DR

This paper investigates sterile neutrinos within a specific extended gauge model, analyzing their potential as dark matter candidates and deriving cosmological bounds based on their thermal history and abundance.

Contribution

It applies cosmological limits to sterile neutrinos in a novel $SU(3)_C\otimes SU(3)_L\otimes SU(3)_R\otimes U(1)_N$ model, providing bounds on model parameters and neutrino properties.

Findings

Sterile neutrinos can be dark matter candidates with keV masses.

Cosmological constraints suggest these neutrinos are hot dark matter.

Bounds on Yukawa couplings and gauge boson masses are derived.

Abstract

We study sterile neutrinos in an extension of the standard model, based on the gauge group $SU(3)_C\otimes SU(3)_L\otimes SU(3)_R\otimes U(1)_N$, and use this model to illustrate how to apply cosmological limits to thermalized particles that decouple while relativistic. These neutrinos, $N_{aL}$, can be dark matter candidates, with a keV mass range arising rather naturally in this model. We analyse the cosmological limits imposed by $N_{eff}$ and dark matter abundance on these neutrinos. Assuming that these neutrinos have roughly equal masses and are not CDM, we conclude that the $N_{eff}$ experimental value can be satisfied in some cases and the abundance constraint implies that these neutrinos are hot dark matter. With this information, we give upper bounds on the Yukawa coupling between the sterile neutrinos and a scalar field, the possible values of the VEV of this scalar field and lower bounds to the mass of one gauge boson of the model.