An Asymmetric SIMP Dark Matter Model

TL;DR

This paper introduces the first asymmetric SIMP dark matter model involving new particles and gauge symmetry breaking, explaining relic density, stability, and potential experimental signatures, with a unique bouncing density effect.

Contribution

It presents a novel asymmetric SIMP dark matter model with accidental symmetries, a bouncing density effect, and testable predictions for future experiments.

Findings

Relic density determined by 3→2 and 2→2 processes.

DM stability from accidental $ ext{Z}_4$ charges after symmetry breaking.

Predicted DM-electron scattering cross section for future detection.

Abstract

In this paper, we construct the first asymmetric strongly interacting massive particles (SIMP) dark matter (DM) model, where a new vector-like fermion and a new complex scalar both having nonzero chemical potentials can be asymmetric DM particles. After the spontaneous breaking of a U(1)$^{}_\textsf{D}$ dark gauge symmetry, these two particles can have accidental $\mathbb{Z}^{}_4$ charges making them stable. By adding one more complex scalar as a mediator between the SIMP DM, the relic density of DM is determined by $3 \to 2$ and two-loop induced $2 \to 2$ annihilations in this model. On the other hand, the SIMP DM can maintain kinetic equilibrium with the thermal bath until the DM freeze-out temperature via the new gauge interaction. Interestingly, this model can have a bouncing effect on DM, whereby the DM number density rises after the chemical freeze-out of DM. With this effect, the prediction of the DM self-interacting cross section in this model can be consistent with astrophysical observations, and the ratio of the DM energy density to the baryonic matter energy density can be explained by primordial asymmetries. We also predict the DM-electron elastic scattering cross section that can be used to test this model in future projected experiments.