The search for neutrino oscillations in the appearance mode νν→νe for neutrino energies near the muon threshold

Abstract A search for neutrino oscillations in the appearance mode ν ν → ν e was performed using the in-flight pion-decay neutrino source at the LAMPF accelerator. An all-active scintillator detector was exposed to a muon-neutrino beam produced by five Coulombs of 800 MeV protons on target. Oscillations events would have appeared as high-energy electrons from the reaction ν e +C→e − +X. We also measured charged-current muons events in the detector to normalize our results. Our data show no evidence for neutrino oscillations and we place 90% CL upper limits on sin 2 (2 φ ) Δm 2 = 11 eV 2 , and Δm 2 2 for complete mixing.