Solar constraints on hidden photons re-visited

Understand

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.