Decay of photon with high as well as low energy
  The decay of photon by the influence of magnetic field is considered. It is shown here that if the photon energy is grater than 1 MeV then photon can decay electron positron pair, but if it remains below 1 MeV then photon decays into neutrino antineutrino pair. The decay rates for both of the processes are calculated. All possible Feynman diagrams are taken into account to construct the matrix element for either of the processes. In the second process all three type of neutrinos are considered. The significance of these processes are discussed briefly. 
Indranath Bhattacharyya
hep-ph