On search for hidden sector photons in Super-Kamiokande
  If hidden sector photons exist, they could be produced through oscillations of photons emitted by the Sun. We show that a search for these particles could be performed in Super-Kamiokande due to the presence in this detector of a large number of photomultiplier's (PMTs) with a relatively low noise and big size. These particles would penetrate the Earth shielding and would be detected by PMTs through their oscillations into real photons inside the PMTs vacuum volume. This would results in an increase of the PMT counting rate and it daily variations depending on the Earth position with respect to the Sun. The proposed search for this effect is sensitive to the photon-hidden photon mixing strength as small as ~10^{-6} for the hidden photon mass region ~10^{-3} - 10^{-1} eV and, in the case of nonobservation, could improve limits recently obtained from photon regeneration laser experiments for this mass region. 
S.N. Gninenko