Towards Cogenesis via Asymmetric Freeze-in: The $\chi$ Who Came-in from the Cold

TL;DR

This paper explores asymmetric freeze-in as a mechanism for dark matter cogenesis, demonstrating that out-of-equilibrium mediators can generate significant particle asymmetries, addressing previous limitations.

Contribution

It introduces a simple scalar model with an out-of-equilibrium mediator to show how sizeable asymmetries can be produced in AFI scenarios.

Findings

Out-of-equilibrium mediators enable larger asymmetries.

Feeble portal interactions can still produce significant dark matter asymmetry.

The model overcomes previous cancellations limiting asymmetry generation.

Abstract

In models of freeze-in the dark matter (DM) is decoupled from the visible sector and initially has a depleted number density. The hidden and visible sectors are connected only via a feeble portal interaction by which DM can be produced. Asymmetric freeze-in (AFI) combines this scenario with ideas from asymmetric DM and provides a potential cogenesis mechanism. However, it has been argued that existing AFI models do not produce suitably large particle asymmetries due to cancellations which arises because the mediator state remains in thermal equilibrium. We examine AFI via an out-of-equilibrium mediator and using a simple scalar model show that in this case sizeable asymmetries may be generated.