Event Excess in the MiniBooNE Search for ${\bar{\nu }}_{\mu }\to {\bar{\nu }}_e$ Oscillations

Abstract

The MiniBooNE experiment at Fermilab reports results from a search for ${\bar{\nu }}_{\mu }\to {\bar{\nu }}_e$ oscillations, using a data sample corresponding to $5.66\times 10^{20}$ protons on target. An excess of $20.9\pm 14.0$ events is observed in the energy range $475<E_{\nu }^{QE}<1250$ MeV, which, when constrained by the observed ${\bar{\nu }}_{\mu }$ events, has a probability for consistency with the background-only hypothesis of 0.5\%. On the other hand, fitting for ${\bar{\nu }}_{\mu }\to {\bar{\nu }}_e$ oscillations, the best-fit point has a ${\chi }^2$-probability of 8.7\%. The data are consistent with ${\bar{\nu }}_{\mu }\to {\bar{\nu }}_e$ oscillations in the 0.1 to 1.0 eV${}^2$ $\Delta m^2$ range and with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory.

Comments: Revised abstract