a Search for Neutrino Oscillations in a Muon Neutrino Beam at Brookhaven National Laboratory

The phenomenon of neutrino oscillations was studied with the use of the muon neutrino beam generated by the proton synchrotron (AGS) at Brookhaven National Laboratory, operated at 28.3 GeV/c. The analysis is conducted on the totality of accumulated interactions with at least one electromagnetic shower in the final state and leads to the observation of 38.5 +/- 14.4 (stat) +/- 10.2 (syst) excess events attributed to electron neutrino interactions. The excess is at the level of 2.7 +/- 0.7 standard deviations. If this result is interpreted as neutrino oscillations then in the sin^22theta- delta m ^2 plane of oscillations for the v _muto v_{e} channel it allows values of delta m^2 between 1 and 10 eV^2 and 1% for sin^22theta. Other interpretations are also possible.