WHEN DO NEUTRINOS CEASE TO OSCILLATE

In order to investigate when neutrinos cease to oscillate in the frame work of quantum field theory, we have reexamined the wave packet treat ment of neutrino oscillations by taking different sizes of the wave pa ckets of the particles involved in the production and detection proces ses. The treatment is shown to be considerably simplified by using the Grimus-Stockinger theorem which enables us to carry out the integrati on over the momentum of the propagating neutrino. Our new results conf irm the recent observation by Kiers, Nussinov and Weiss that a precise measurement of the energies of the particles involved in the detectio n process would increase the coherence length. We also present a preci se definition of the coherence length beyond which neutrinos cease to oscillate. (C) 1998 Elsevier Science B.V.