The temporal and spatial coherence widths of the microscopic process by which a neutrino is detected are incorporated in the quantum mechanical wave packet treatment of neutrino oscillations, confirming the observation of Kiers, Nussinov and Weiss that an accurate measurement of the energies of the particles participating in the detection process can increase the coherence length. However, the wave packet treatment presented here shows that the coherence length has an upper bound, determined by the neutrino energy and the mass-squared difference, beyond which the coherence of the oscillation process is lost.Comment: 7 pages, no figures. The case of a large temporal coherence width of the detector is clarifie

We calculate the one-loop thermal self-energy of a neutrino in a constant and homogeneous magnetic field to all orders in the magnetic field strength using Schwinger's proper time method. We obtain the dispersion relation under various conditions. ͓S0556-2821͑98͒08618-4͔PACS number͑s͒: 14.60.Pq, 95.30.Cq

We have studied the constraints imposed by the results of neutrino oscillation experiments on the effective Majorana mass | m | that characterizes the contribution of Majorana neutrino masses to the matrix element of neutrinoless double-beta decay. We have shown that in a general scheme with three Majorana neutrinos and a hierarchy of neutrino masses (which can be explained by the see-saw mechanism), the results of neutrino oscillation experiments imply rather strong constraints on the parameter | m |. From the results of the first reactor long-baseline experiment CHOOZ and the Bugey experiment it follows that | m | 3 × 10 −2 eV if ∆m 2 2eV 2 (∆m 2 is the largest mass-squared difference). Hence, we conclude that the observation of neutrinoless doublebeta decay with a probability that corresponds to | m | 10 −1 eV would be 1 a signal for a non-hierarchical neutrino mass spectrum and/or non-standard mechanisms of lepton number violation. PACS number(s): 14.60.Pq, 23.40.-s Typeset using REVT E X 2