Solar constraints on hidden photons re-visited

TL;DR

This paper re-evaluates solar emission constraints on hidden photons, calculating emission rates with thermal field theory, and derives a new, more restrictive limit on the kinetic mixing parameter, impacting dark matter detection prospects.

Contribution

It provides a revised calculation of solar hidden photon emission rates using thermal field theory and kinetic equations, leading to the most restrictive stellar limit for low-mass hidden photons.

Findings

New bound  on kinetic mixing parameter  eV/m for m < 3 eV

Resonant emission rates are enhanced by plasma effects, consistent with previous studies

Future experiments like XENON10 and ALPS-II could detect or further constrain hidden photons.

Abstract

We re-examine solar emission of hidden photons gamma' (mass m) caused by kinetic mixing. We calculate the emission rate with thermal field theory methods and with a kinetic equation that includes "flavor oscillations" and photon absorption and emission by the thermal medium. In the resonant case both methods yield identical emission rates which, in the longitudinal channel, are enhanced by a factor w_P^2/m^2 (plasma frequency w_P) in agreement with An, Pospelov and Pradler (2013). The Sun must not emit more energy in a "dark channel" than allowed by solar neutrino measurements, i.e., not more than 10% of its photon luminosity. Together with the revised emission rate, this conservative requirement implies a bound \chi<4\times 10^-12 eV/m for the kinetic mixing parameter. This is the most restrictive stellar limit below m ~ 3 eV, whereas for larger masses the transverse channel dominates together with limits from other stars. A recent analysis of XENON10 data marginally improves the solar limit, leaving open the opportunity to detect solar hidden photons with future large-scale dark matter experiments. Detecting low-mass hidden photons with the ALPS-II photon-regeneration experiment also remains possible.