Astrophysical searches for a hidden-photon signal in the radio regime

TL;DR

This paper explores how radio observations can detect or constrain hidden photons, hypothetical particles predicted by extensions of the Standard Model, by analyzing their potential effects on radio spectra of astrophysical sources.

Contribution

It develops search methods for hidden photons in the radio regime, analyzing sensitivity factors and proposing ways to improve detection prospects with future facilities.

Findings

Radio observations can probe hidden photon kinetic mixing down to ~10^-3.

Sensitivity extends to hidden photon masses as low as ~10^-17 eV.

Future radio telescopes and data stacking could enhance detection capabilities.

Abstract

Common extensions of the Standard Model of particle physics predict the existence of a "hidden" sector that comprises particles with a vanishing or very weak coupling to particles of the Standard Model (visible sector). For very light (m < 10^-14 eV) hidden U(1) gauge bosons (hidden photons), broad-band radio spectra of compact radio sources could be modified due to weak kinetic mixing with radio photons. Here, search methods are developed and their sensitivity discussed, with specific emphasis on the effect of the coherence length of the signal, instrumental bandwidth, and spectral resolution. We conclude that radio observations in the frequency range of 0.03--1400 GHz probe kinetic mixing of ~10^-3 of hidden photons with masses down to ~10^-17 eV. Prospects for improving the sensitivity with future radio astronomical facilities as well as by stacking data from multiple objects are discussed.