Beam dump experiments and neutrino oscillations

Electron-muon universality requires the electron - to muon-neutrino flux ratio in prompt neutrino experiments to be unity independently of the production mechanism. The presently available data indicate that the confidence level for this to be true is only 2.10-4. The consistency of the measurements at various dump-detector distances suggests an interpretation of the data in terms of neutrino oscillations. When this hypothesis is tried on the most recent ('81 - '82) data a fit is obtained with the parameters Δm2 = (360+-40) eV2 sin2(2α) = 0.32 -0.08+0.18 and a confidence level of about 30%. The results of older prompt neutrino as well as those of other experiments are shown to be in agreement with this result. It is concluded that electron - to tau-neutrino oscillations represent a completely reasonable interpretation of the present prompt neutrino data