Nonthermal dark matter models and signals

TL;DR

This paper proposes two nonthermal dark matter models where relic density arises from decay of metastable particles, predicting sharp gamma-ray signals and analyzing their consistency with various experimental constraints.

Contribution

It introduces two novel nonthermal dark matter models involving decay of metastable particles, expanding beyond traditional WIMP scenarios.

Findings

Sharp gamma-ray emission as an indirect detection signal.

Parameter space constraints from gamma-ray observations and relic density.

Some parameter regions are already ruled out by existing gamma-ray data.

Abstract

Many experiments exploring weakly interacting massive particles (WIMPs) such as direct, indirect and collider searches have been carried out until now. However, a clear signal of a WIMP has not been found yet and it makes us to suspect that WIMPs are questionable as a dark matter candidate. Taking into account this situation, we propose two models in which dark matter relic density is produced by decay of a metastable particle. In the first model, the metastable particle is a feebly interacting massive particle, which is the so-called FIMP produced by freeze-in mechanism in the early universe. In the second model, the decaying particle is thermally produced the same as the usual WIMP. However decay of the particle into dark matter is led by a higher dimensional operator. As a phenomenologically interesting feature of nonthermal dark matter discussed in this paper, a strong sharp gamma-ray emission as an indirect detection signal occurs due to internal bremsstrahlung, although some parameter space has already been ruled out by this process. Moreover combining other experimental and theoretical constraints such as dark matter relic density, big bang nucleosynthesis, collider, gamma-rays and perturbativity of couplings, we discuss the two nonthermal DM models.