Solar chameleons: Novel channels

TL;DR

This paper refines the calculation of solar chameleon particle flux by including overlooked processes, establishing a new upper limit on their photon coupling, and highlighting their potential detectability in future helioscopes.

Contribution

It introduces a comprehensive analysis of solar chameleon production, considering new processes and magnetic field effects, leading to a tighter constraint on chameleon-photon coupling.

Findings

Upper limit on chameleon-photon coupling: β_γ ≲ 10^{10}

Revised solar chameleon flux calculations

Potential detectability in next-generation helioscopes

Abstract

We revisit the flux of chameleons (light scalar particles which could play a role in the dark energy phenomenon) produced in the interior of the Sun. Our novel analysis incorporates various important details and new processes that have previously been overlooked, including the impact of the bulk magnetic field profile, as well as Primakoff production of chameleons in the electric fields of electrons and ions. In this paper we consider only the contributions of transverse photons. The production of chameleons from longitudinal electromagnetic excitations will be presented in a dedicated follow-up work. Demanding that the total flux of chameleons does not exceed 3% of the solar luminosity leads to the stringent upper limit on the chameleon-photon conformal coupling $\beta_\gamma \lesssim 10^{10}$, assuming that the height of the chameleon potential is set to the dark energy scale $\Lambda = 2.4$ meV, and independently of other couplings to matter. Although this bound is tighter than current upper limits on $\beta_{\gamma}$ from the CAST helioscope, these limits will have to be reassessed in terms of the updated solar chameleon flux we have computed. We argue that solar chameleons, potentially detectable in next-generation helioscopes such as IAXO, can be used to probe a region of chameleon parameter space that has yet to be covered.