Edges and Endpoints in 21-cm Observations from Resonant Photon Production

TL;DR

This paper proposes a new method to detect physics beyond the Standard Model by identifying spectral edges and endpoints in 21-cm observations caused by resonant dark photon-to-photon conversions during cosmic dawn and dark ages.

Contribution

It introduces the concept of spectral edges and endpoints as signatures in 21-cm data resulting from dark sector interactions, specifically through kinetically mixed dark photons.

Findings

Spectral features can be imprinted by resonant dark photon conversions.

These signatures provide a new observational window into dark sector physics.

Implications for current and future 21-cm experiments are discussed.

Abstract

We introduce a novel class of signatures---spectral edges and endpoints---in 21-cm measurements resulting from interactions between the standard and dark sectors. Within the context of a kinetically mixed dark photon, we demonstrate how resonant dark photon-to-photon conversions can imprint distinctive spectral features in the observed 21-cm brightness temperature, with implications for current, upcoming, and proposed experiments targeting the cosmic dawn and the dark ages. These signatures open up a qualitatively new way to look for physics beyond the Standard Model using 21-cm observations.