TREATMENT OF NEUTRINO OSCILLATIONS WITHOUT RESORT TO WEAK EIGENSTATES

We discuss neutrino oscillations in the framework of the quantum field theory without introducing the concept of neutrino weak eigenstates. The external particles are described by wave packets and the different mass eigenstate neutrinos propagate between the production and detect ion interactions, which are macroscopically localized in space-time. T he time-averaged cross section, which is the measurable quantity in th e usual experimental setting, is calculated. It is shown that only in the extremely relativistic limit can the usual quantum mechanical osci llation probability be factored out of the cross section.