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

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 thorn 1 active-to -sterile neutrino oscillation framework. We analyze the neutrino candidate events for the recent measurements of charged-current nu e and nu mu interactions in the MicroBooNE detector, using data corresponding to an exposure of 6.37 x 1020 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 Delta m241 and the sterile neutrino mixing angles theta mu e and theta ee, excluding part of the parameter space allowed by experimental anomalies. Cancellation of nu e appearance and nu e disappearance effects due to the full 3 thorn 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.

Automated summary

In this study, we searched for eV-scale sterile neutrino oscillations using the MicroBooNE liquid argon detector, considering all possible appearance and disappearance effects within the 3+1 active-to-sterile neutrino oscillation framework. By analyzing the recent measurements of charged-current νe and νμ interactions in the MicroBooNE detector, we observed no evidence of light sterile neutrino oscillations. We derived exclusion contours at the 95% confidence level and discussed the degeneracy issue in determining the oscillation parameters.