Atlas of solar hidden photon emission

TL;DR

This paper provides a comprehensive calculation of the flux of hidden photons emitted by the Sun across a broad mass and energy range, crucial for guiding experimental searches for dark matter.

Contribution

It offers the most complete atlas of solar hidden photon emission, including detailed modeling of photon-HP oscillations and resonance effects in the solar environment.

Findings

Resonance oscillations significantly influence HP flux predictions.

The emission region is a thin spherical shell with distinctive angular distribution.

Results cover HP masses from 0 to 1 keV and energies from IR to X-ray.

Abstract

Hidden photons, gauge bosons of a U(1) symmetry of a hidden sector, can constitute the dark matter of the universe and a smoking gun for large volume compactifications of string theory. In the sub-eV mass range, a possible discovery experiment consists on searching the copious flux of these particles emitted from the Sun in a helioscope setup \`a la Sikivie. In this paper, we compute the flux of transversely polarised HPs from the Sun, a necessary ingredient for interpreting such experiments. We provide a detailed exposition of photon-HP oscillations in inhomogenous media, with special focus on resonance oscillations, which play a leading role in many cases. The region of the Sun emitting HPs resonantly is a thin spherical shell for which we justify an averaged-emission formula and which implies a distinctive morphology of the angular distribution of HPs on Earth in many cases. Low mass HPs with energies in the visible and IR have resonances very close to the photosphere where the solar plasma is not fully ionised and requires building a detailed model of solar refraction and absorption. We present results for a broad range of HP masses (from 0-1 keV) and energies (from the IR to the X-ray range), the most complete atlas of solar HP emission to date.