Event Excess in the MiniBooNE Search for $\bar \nu_\mu \rightarrow \bar \nu_e$ Oscillations

TL;DR

The MiniBooNE experiment observed an excess of events suggesting possible antineutrino oscillations, providing evidence consistent with oscillation models in the 0.1 to 1.0 eV^2 mass-squared difference range.

Contribution

This paper reports the first detailed search for antineutrino oscillations in MiniBooNE, highlighting an excess of events and supporting evidence for oscillations in a specific mass-squared difference range.

Findings

Observed an excess of 20.9 ± 14.0 events in the energy range 475-1250 MeV.

Data are consistent with antineutrino oscillations in the 0.1 to 1.0 eV^2 Δm^2 range.

The results support previous evidence of antineutrino oscillations from other experiments.

Abstract

The MiniBooNE experiment at Fermilab reports results from a search for $\bar \nu_\mu \rightarrow \bar \nu_e$ 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 $\bar{\nu}_{\mu}\rightarrow\bar{\nu}_e$ oscillations, the best-fit point has a $\chi^2$-probability of 8.7\%. The data are consistent with $\bar \nu_\mu \rightarrow \bar \nu_e$ 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.