Event Excess in the MiniBooNE Search for ν̅ μ→ν̅ e Oscillations

Abstract

The MiniBooNE experiment at Fermilab reports results from a search for ν̅ μ→ν̅ e [nu overscore subscript mu→nu overscore subscript e] oscillations, using a data sample corresponding to 5.66×10 20 [suprscript 20] protons on target. An excess of 20.9±14.0 events is observed in the energy range 475<EνQE [E superscript QE subscript nu] <1250 MeV, which, when constrained by the observed ν̅ μ [nu overscore subscript mu] events, has a probability for consistency with the background-only hypothesis of 0.5%. On the other hand, fitting for ν̅ μ→ν̅ e [nu overscore subscript mu→nu overscore subscript e] oscillations, the best-fit point has a χ2 [X superscript 2] probability of 8.7%. The data are consistent with ν̅ μ→ν̅ e [nu overscore subscript mu→nu overscore subscript e] oscillations in the 0.1 to 1.0 eV2 Δm2 [eV superscript 2 delta m superscript 2] range and with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory.