We analyze neutrino oscillations in a thought experiment in which neutrinos are produced by electrons on target nuclei. The neutrinos are detected through charged lepton production in their collision with nuclei in detector. Both the target and the detector are assumed to be crystals. The neutrinos are described by propagators. We find that different neutrino mass eigenstates have equal energies. We reproduce the standard phase of oscillations and demonstrate that at large distance from the production point oscillations disappear

We consider a thought experiment, in which a neutrino is produced by an electron on a nucleus in a crystal. The wave function of the oscillating neutrino is calculated assuming that the electron is described by a wave packet. If the electron is relativistic and the spatial size of its wave packet is much larger than the size of the crystal cell, then the wave packet of the produced neutrino has essentially the same size as the wave packet of the electron. We investigate the suppression of neutrino oscillations at large distances caused by two mechanisms: 1) spatial separation of wave packets corresponding to different neutrino masses; 2) neutrino energy dispersion for given neutrino mass eigenstates. We resolve contributions of these two mechanisms. *