Light Thermal Self-Interacting Dark Matter in the Shadow of Non-Standard Cosmology

TL;DR

This paper presents a model for GeV-scale self-interacting dark matter produced thermally, incorporating a new dark gauge interaction and non-standard cosmology to satisfy relic abundance and self-interaction constraints.

Contribution

It introduces a novel dark matter model with specific particles and interactions, and explores its viability within a non-standard cosmological framework.

Findings

The model can produce the correct relic abundance and self-interaction strength.

Dark gauge boson decays into active neutrinos help evade CMB bounds.

Non-standard cosmology allows compatibility with observational constraints.

Abstract

In this paper, we construct a viable model for a GeV scale self-interacting dark matter (DM), where the DM was thermally produced in the early universe. Here, a new vector-like fermion with a dark charge under the $U(1)_{D}$ gauge symmetry serves as a secluded WIMP DM and it can dominantly annihilate into the light dark gauge boson and singlet scalar through the dark gauge interaction. Also, the self-interaction of DM is induced by the light dark gauge boson via the same gauge interaction. In addition to these particles, we further introduce two Weyl fermions and a doublet scalar, by which the dark gauge boson produced from s-wave DM annihilations can mostly decay into active neutrinos after the dark symmetry breaking such that the CMB bound on the DM with low masses can be eluded. In order to have a common parameter region to explain the observed relic abundance and self-interaction of DM, we also study this model in a non-standard cosmological evolution, where the cosmic expansion driven by a new field species is faster than the standard radiation-dominated universe during the frozen time of DM. Reversely, one can also use the self-interacting nature of light thermal DM to examine the non-standard cosmological history of the universe.