Secluded WIMP Dark Matter

TL;DR

This paper explores a mechanism where WIMP dark matter decouples from the Standard Model via metastable mediators, resulting in suppressed direct detection signals but potentially observable gamma-ray signatures.

Contribution

It introduces a generic secluded WIMP model with metastable mediators, analyzing its phenomenology and observational constraints across different mass scales.

Findings

WIMP can be secluded with very small elastic scattering cross-section.

Indirect gamma-ray signals remain observable and consistent with weak-scale annihilation.

Severe constraints from gamma-ray and flavor physics on MeV-scale models.

Abstract

We consider a generic mechanism via which thermal relic WIMP dark matter may be decoupled from the Standard Model, namely through a combination of WIMP annihilation to metastable mediators with subsequent delayed decay to Standard Model states. We illustrate this with explicit examples of WIMPs connected to the Standard Model by metastable bosons or fermions. In all models, provided the WIMP mass is greater than that of the mediator, it can be secluded from the Standard Model with an extremely small elastic scattering cross-section on nuclei and rate for direct collider production. In contrast, indirect signatures from WIMP annihilation are consistent with a weak scale cross-section and provide potentially observable \gamma-ray signals. We also point out that \gamma-ray constraints and flavor physics impose severe restrictions on MeV-scale variants of secluded models, and identify limited classes that pass all the observational constraints.