New experimental limits on νμ→νe oscillations

Abstract The results of an experiment which searched for ν e events arising from oscillations of a low-energy ν μ beam are presented. The BEBC heavy liquid bubble chamber, placed at a distance of 825 m from an external proton target at the CERN PS, was used as a neutrino detector. The appearance of ν e CC interactions provides a sensitive indication of ν μ → ν e oscillations. 470 ν μ CC events and 4 ν e events, with an estimated background of 3 ν c CC events, have been observed. The resulting limits on the oscillation parameters are: δm 2 ⩽0.09 eV 2 (for maximal mixing) and sin 2 θ ⩽0.013 for δm 2 =2.2 eV 2 , at the 90% confidence level.