Evidence for µ ! e Neutrino Oscillations from LSND

A search for �µ ! �e oscillations has been conducted with the LSND ap- paratus at the Los Alamos Meson Physics Facility. Using �µ from � + de- cay in flight, thee appearance is detected via the charged-current reaction �e C ! e − X. Two independent analyses observe a total of 40 beam-on high-energy electron events (60 < Ee < 200 MeV) consistent with the above signature. This number is significantly above the 21.9 ± 2.1 events expected from thee contamination in the beam and the beam-off background. If interpreted as an oscillation signal, the observed oscillation probability of (2.6 ± 1.0 ± 0.5) × 10 −3 is consistent with the previously reported ¯ �µ ! ¯ �e