Annihilation of an electron-positron pair into a neutrino pair in a constant external field

An exact expression for the probability of the annihilation of the electron-positron pair into the neutrino pair is obtained in the low-energy approximation of the Weinberg–Salam model. The reaction is considered in a constant external field. It is shown that significant oscillations of the probability take place with the increasing of the intensity of the field.