A Combined $ν_μ\to ν_e$ and $\barν_μ\to \barν_e$ Oscillation Analysis of the MiniBooNE Excesses

Abstract

The MiniBooNE experiment at Fermilab reports results from an analysis of the combined $ν_e$ and $\bar ν_e$ appearance data from $6.46 \times 10^{20}$ protons on target in neutrino mode and $11.27 \times 10^{20}$ protons on target in antineutrino mode. A total excess of $240.3 \pm 34.5 \pm 52.6$ events ($3.8 σ$) is observed from combining the two data sets in the energy range $200<E_ν^{QE}<1250$ MeV. In a combined fit for CP-conserving $ν_μ\rightarrow ν_e$ and $\barν_μ\rightarrow\barν_e$ oscillations via a two-neutrino model, the background-only fit has a $χ^2$-probability of 0.03% relative to the best oscillation fit. The data are consistent with neutrino oscillations in the $0.01 < Δm^2 < 1.0$ eV$^2$ range and with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector (LSND).

Figures (5)

• Figure 1: The neutrino mode (top) and antineutrino mode (bottom) $E_\nu^{QE}$ distributions for ${\nu}_e$ CCQE data (points with statistical errors) and background (histogram with systematic errors).
• Figure 2: The neutrino mode (top) and antineutrino mode (bottom) event excesses as a function of $E_\nu^{QE}$. Also shown are the expectations from the best two-neutrino and 3+2 joint oscillation fits with $200<E_\nu^{QE}<3000$ MeV and from two reference values in the LSND allowed region. All known systematic errors are included in the systematic error estimate.
• Figure 3: The oscillation probability as a function of $L/E_\nu^{QE}$ for $\nu_\mu \rightarrow \nu_e$ and $\bar{\nu}_\mu \rightarrow \bar{\nu}_e$ candidate events from MiniBooNE and $\bar{\nu}_\mu \rightarrow \bar{\nu}_e$ candidate events from LSND. The data points include both statistical and systematic errors. Also shown are the oscillation probabilities from the two-neutrino and 3+2 joint oscillation fits.
• Figure 4: MiniBooNE allowed regions in neutrino mode (top) and antineutrino mode (bottom) for events with $E^{QE}_{\nu} > 200$ MeV within a two-neutrino ${\nu}_{\mu}\rightarrow{\nu}_e$ and $\bar{\nu}_{\mu}\rightarrow\bar{\nu}_e$ oscillation model. Also shown is the $\bar{\nu}_{\mu}\rightarrow\bar{\nu}_e$ limit from the KARMEN experiment karmen. The shaded areas show the 90% and 99% C.L. LSND $\bar{\nu}_{\mu}\rightarrow\bar{\nu}_e$ allowed regions. The black stars show the best fit points, while the crosses show LSND reference values.
• Figure 5: MiniBooNE allowed regions in combined neutrino and antineutrino mode for events with $200<E^{QE}_{\nu}< 3000$ MeV within a two-neutrino ${\nu}_{\mu}\rightarrow{\nu}_e$ and $\bar{\nu}_{\mu}\rightarrow\bar{\nu}_e$ oscillation model. Also shown is the $\bar{\nu}_{\mu}\rightarrow\bar{\nu}_e$ limit from the KARMEN experiment karmen. The shaded areas show the 90% and 99% C.L. LSND $\bar{\nu}_{\mu}\rightarrow\bar{\nu}_e$ allowed regions. The black star shows the best fit point.