Helioscope Bounds on Hidden Sector Photons

TL;DR

This paper derives constraints on hidden photons from solar flux calculations and helioscope data, setting limits on their kinetic mixing with standard photons, especially at low masses, and highlighting the sensitivity of axion helioscopes to these particles.

Contribution

It provides new bounds on hidden photon parameters using solar flux models and helioscope data, including the impact of longitudinal polarization at low masses.

Findings

Limits on kinetic mixing parameter down to 10^-14 for certain masses

Helioscopes like CAST constrain low-mass hidden photons

Longitudinal hidden photons at low energies are challenging to detect

Abstract

The flux of hypothetical "hidden photons" from the Sun is computed under the assumption that they interact with normal matter only through kinetic mixing with the ordinary standard model photon. Requiring that the exotic luminosity is smaller than the standard photon luminosity provides limits for the mixing parameter down to 10^-14, depending on the hidden photon mass. Furthermore, it is pointed out that helioscopes looking for solar axions are also very sensitive to hidden photons. The recent results of the CAST collaboration are used to further constrain the mixing parameter at low masses m<1 eV where the luminosity bound is weaker. In this regime the solar hidden photon flux has a sizable contribution of longitudinally polarized hidden photons of low energy which are invisible for current helioscopes.