A composite solution to the EDGES anomaly

TL;DR

This paper proposes a composite model of millicharged dark matter blobs that can explain the EDGES anomaly while evading cosmological and stellar constraints, expanding the viable parameter space for detection.

Contribution

It introduces a novel composite blob model of millicharged dark matter that reconciles the EDGES anomaly with existing constraints.

Findings

Large parameter space for millicharged blobs remains viable.

Model allows for new low-momentum transfer detection methods.

Salvages previous models by considering composite structures.

Abstract

Subcomponent millicharged dark matter that cools baryons via Coulomb interactions has been invoked to explain the EDGES anomaly. However, this model is in severe tension with constraints from cosmology and stellar emissions. In this work, we consider the consequences of these millicharged particles existing in composite blobs. The relevant degrees of freedom at high temperature are minuscule elementary charges, which fuse at low temperatures to make up blobs of larger charge. These blobs serve as the degrees of freedom relevant in cooling the baryons sufficiently to account for the EDGES anomaly. In such a model, cosmology and stellar constraints (which involve high-temperature processes) apply only to the feebly-interacting elementary charges and not to the blobs. This salvages a large range of parameter space for millicharged blobs that can explain the EDGES anomaly. It also opens up new parameter space for direct detection, albeit at low momentum transfers.