Non-thermal Production of Minimal Dark Matter via Right-handed Neutrino Decay

TL;DR

This paper explores a non-thermal dark matter production mechanism via right-handed neutrino decay in minimal dark matter models, allowing for lower dark matter masses compatible with observational constraints.

Contribution

It introduces a model where dark matter is produced non-thermally through right-handed neutrino decay, reducing the required dark matter mass in minimal dark matter scenarios.

Findings

Dark matter can be non-thermally produced by right-handed neutrino decay.

Specific dark matter mass ranges are identified to satisfy gamma-ray observational bounds.

Sommerfeld corrections significantly influence the viable parameter space.

Abstract

Minimal Dark Matter (MDM) stands as one of the simplest dark matter scenarios. In MDM models, annihilation and co-annihilation processes among the members of the MDM multiplet are usually very efficient, pushing the dark matter mass above $\mathcal{O}(10)$ TeV in order to reproduce the observed dark matter relic density. Motivated by this little drawback, in this paper we consider an extension of the MDM scenario by three right-handed neutrinos. Two specific choices for the MDM multiplet are studied: a fermionic $SU(2)_L$ quintuplet and a scalar $SU(2)_L$ septuplet. The lightest right-handed neutrino, with tiny Yukawa couplings, never reaches thermal equilibrium in the early universe and is produced by freeze-in. This creates a link between dark matter and neutrino physics: dark matter can be non-thermally produced by the decay of the lightest right-handed neutrino after freeze-out, allowing to lower significantly the dark matter mass. We discuss the phenomenology of the non-thermally produced MDM and, taking into account significant Sommerfeld corrections, we find that the dark matter mass must have some specific values in order not to be in conflict with the current bounds from gamma-ray observations.