Results on ν μ → ν e Neutrino Oscillations from the LSND Experiment

A search for ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}$ oscillations has been conducted with the LSND apparatus using ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ from ${\ensuremath{\pi}}^{+}$ decay in flight. Two analyses observe a total of 40 beam-on high-energy (60--200 MeV) electron events consistent with the ${\ensuremath{\nu}}_{e}\mathrm{C}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}X$ inclusive reaction. This number is significantly above the $21.9\ifmmode\pm\else\textpm\fi{}2.1$ events expected from the ${\ensuremath{\nu}}_{e}$ contamination in the beam and the beam-off background. If interpreted as an oscillation signal, the observed oscillation probability of $(2.6\ifmmode\pm\else\textpm\fi{}1.0\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ is consistent with the previously reported ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{e}$ oscillation evidence from LSND.