On search for eV hidden sector photons in Super-Kamiokande and CAST   experiments
  If light hidden sector photons exist, they could be produced through kinetic mixing with solar photons in the eV energy range. We propose to search for this hypothetical hidden photon flux with the Super-Kamiokande and/or upgraded CAST detectors. The proposed experiments are sensitive to mixing strengths as small as 10^-9 for hidden photon masses in the sub eV region and, in the case of non-observation, would improve limits recently obtained from photon regeneration laser experiments in this mass region. 
Sergei Gninenko and Javier Redondo