First Constraints on Light Sterile Neutrino Oscillations from Combined Appearance and Disappearance Searches with the MicroBooNE Detector

Abstract

We present a search for eV-scale sterile neutrino oscillations in the MicroBooNE liquid argon detector, simultaneously considering all possible appearance and disappearance effects within the $3+1$ active-to-sterile neutrino oscillation framework. We analyze the neutrino candidate events for the recent measurements of charged-current ${\ensuremath{\nu}}_{e}$ and ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ interactions in the MicroBooNE detector, using data corresponding to an exposure of $6.37\ifmmode\times\else\texttimes\fi{}{10}^{20}$ protons on target from the Fermilab booster neutrino beam. We observe no evidence of light sterile neutrino oscillations and derive exclusion contours at the 95% confidence level in the plane of the mass-squared splitting $\mathrm{\ensuremath{\Delta}}{m}_{41}^{2}$ and the sterile neutrino mixing angles ${\ensuremath{\theta}}_{\ensuremath{\mu}e}$ and ${\ensuremath{\theta}}_{ee}$, excluding part of the parameter space allowed by experimental anomalies. Cancellation of ${\ensuremath{\nu}}_{e}$ appearance and ${\ensuremath{\nu}}_{e}$ disappearance effects due to the full $3+1$ treatment of the analysis leads to a degeneracy when determining the oscillation parameters, which is discussed in this Letter and will be addressed by future analyses.