Scalar Multiplet Dark Matter in a Fast Expanding Universe: resurrection of the desert region

TL;DR

This paper investigates how a faster early Universe expansion affects scalar $SU(2)_L$ multiplet dark matter, reviving previously excluded parameter regions and suggesting new collider search strategies.

Contribution

It demonstrates that a faster pre-BBN expansion can reopen desert regions for scalar $SU(2)_L$ multiplet dark matter, expanding the viable parameter space.

Findings

Faster expansion can revive desert regions for scalar DM.

New parameter space compatible with relic density and search bounds.

Potential collider signatures include disappearing or stable charged tracks.

Abstract

We examine the impact of a faster expanding Universe on the phenomenology of scalar dark matter (DM) associated with $SU(2)_L$ multiplets. Earlier works with radiation dominated Universe have reported the presence of desert region for both inert $SU(2)_L$ doublet and triplet DM candidates where the DM is under abundant. We find that the existence of a faster expanding component before BBN can revive a substantial part of the desert parameter space consistent with relic density requirements and other direct and indirect search bounds. We also review the possible collider search prospects of the newly obtained parameter space and predict that such region might be probed at the future colliders with improved sensitivity via a disappearing/stable charged track.