Co-scattering in micrOMEGAs: a case study for the singlet-triplet dark matter model

TL;DR

This paper integrates co-scattering mechanisms into micrOMEGAs and explores their impact on dark matter production in the singlet-triplet model, revealing new parameter space regions and long-lived particle signatures at the LHC.

Contribution

It introduces the co-scattering process into micrOMEGAs and analyzes its effects on dark matter phenomenology in a specific fermionic model.

Findings

Co-scattering is essential for accurate dark matter relic density calculations at very small couplings.

A new parameter space region emerges where co-scattering dominates over co-annihilation.

Long-lived triplet states lead to distinctive signatures constrained by LHC data.

Abstract

In scenarios with very small dark matter (DM) couplings and small mass splittings between the DM and other dark sector particles, so-called "co-scattering" or "conversion-driven freeze-out" can be the dominant mechanism for DM production. We present the inclusion of this mechanism in micrOMEGAs together with a case study of the phenomenological implications in the fermionic singlet-triplet model. For the latter, we focus on the transition between co-annihilation and co-scattering processes. We observe that co-scattering is needed to describe the thermal behaviour of the DM for very small couplings, opening up a new region in the parameter space of the model. The triplet states are often long-lived in this region; we therefore also discuss LHC constraints from long-lived signatures obtained with SModelS.