Radiative transition of a massive neutrino in the field of an intense electromagnetic wave

The radiative transition of a massive neutrino νi→νjγ in the field of a circularly polarized plane electromagnetic wave is studied in the standard model with lepton mixing. A general expression for the decay amplitude is obtained. It is shown that, in contrast to the decay probability in a vacuum or in a constant uniform field, the transition probability in a wave field is free from the threshold factor ∼ (1 - mi/mj). A significant enhancement (∼1033) of the neutrino transition probability in a wave field is discovered. 11 refs., 3 figs