T. Kobilarcik

Improved Search for

The MiniBooNE experiment at Fermilab reports results from an analysis of ν¯e appearance data from 11.27×10²⁰ protons on target in the antineutrino mode, an increase of approximately a factor of 2 over the previously reported results. An event excess of 78.4±28.5 events (2.8σ) is observed in the energy range 200QEν<1250 MeV. If interpreted in a two-neutrino oscillation model, ν¯μ→ν¯e, the best oscillation fit to the excess has a probability of 66% while the background-only fit has a χ² probability of 0.5% relative to the best fit. The data are consistent with antineutrino oscillations in the 0.01<Δm²<1.0 eV² range and have some overlap with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector. All of the major backgrounds are constrained by in situ event measurements so nonoscillation explanations would need to invoke new anomalous background processes. The neutrino mode running also shows an excess at low energy of 162.0±47.8 events (3.4σ) but the energy distribution of the excess is marginally compatible with a simple two neutrino oscillation formalism. Expanded models with several sterile neutrinos can reduce the incompatibility by allowing for CP violating effects between neutrino and antineutrino oscillations.The MiniBooNE experiment at Fermilab reports results from an analysis of the combined

\bar \nu_\mu \rightarrow \bar \nu_e

\nu_e

Oscillations in the MiniBooNE Experiment

and

A Search for electron neutrino appearance at the

\bar \nu_e

\Delta m^{2} \sim 1

appearance data from

eV

6.46 \times 10^{20}

^{2}

protons on target in neutrino mode and

scale

11.27 \times 10^{20}

A Combined

protons on target in antineutrino mode. A total excess of

\nu_\mu \to \nu_e

240.3 \pm 34.5 \pm 52.6