Low-energy neutrino-two-photon interactions

We present a systematic study of low-energy neutrino-two-photon interactions to lowest order of O(αₑₘGF). General structures of such interactions are analyzed. Differences due to whether neutrinos are Dirac particles or Majorana particles are discussed. Simple formulas are derived from which one can easily obtain the corresponding effective neutrino-two-photon interaction in all theoretical models. The compatibility of a small neutrino mass with a large neutrino-two-photon interaction is explored. Some physical implications of such interactions are also examined.