Dark Photons in the Radio Sky: I. Resonant Conversions in Halos

TL;DR

This paper forecasts the potential of the Square Kilometre Array (SKA) radio telescope to detect dark photons through resonant conversions in dark matter halos, which could reveal new physics beyond the Standard Model.

Contribution

It introduces a novel method to detect dark photons using SKA data, forecasting sensitivity improvements over previous Planck-based analyses.

Findings

SKA could detect dark photons with masses between 10^{-13} and 5×10^{-12} eV.

Sensitivity to the kinetic mixing parameter ε could reach as low as ~10^{-8}.

The method could improve detection sensitivity by a factor of 4 compared to previous analyses.

Abstract

Mixing between dark photons and visible photons leads to substantial anisotropies in the cosmic microwave background due to resonant conversions of visible photons into dark photons in baryonic matter found in dark matter halos. In this Letter, we forecast the sensitivity of the Square Kilometre Array (SKA) to this signal. We find that SKA could be the first experiment to discover dark photons with a mass between $10^{-13}$ and $5\times 10^{-12}$ eV and kinetic mixing parameter $\epsilon$ as small as $\sim 10^{-8}$ by cross-correlating their data with a low-redshift galaxy survey, potentially improving on the sensitivity from a similar analysis using Planck data by a factor of 4 in $\epsilon$. This improvement is largely due to an enhancement of the signal at low frequencies and the unique experimental advantages of radio telescopes such as small beam sizes.