Impeded Dark Matter

TL;DR

Impeded Dark Matter explores models with tiny mass splittings that can be positive or negative, affecting annihilation signals and constraints, and introduces specific realizations like vector and composite dark matter.

Contribution

This work introduces the Impeded Dark Matter scenario with small mass splittings, expanding on Forbidden Dark Matter, and demonstrates its natural realization and unique observational signatures.

Findings

Negative mass splitting suppresses annihilation signals, making it insensitive to CMB and dwarf galaxy constraints.

Positive mass splitting suppresses annihilation, allowing light dark matter to evade indirect detection constraints.

Models include vector dark matter from a hidden SU(2) sector and a QCD-like composite dark sector.

Abstract

We consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario "Impeded Dark Matter". We demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden $SU(2)$ sector, and a composite dark matter scenario based on a QCD-like dark sector.