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 $\hat{I}{½}_e$ and $\hat{I}{½}_{\hat{I}}¼$ interactions in the MicroBooNE detector, using data corresponding to an exposure of 6.37$\times$10${}^{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 $\hat{I}”m_{41}^2$ and the sterile neutrino mixing angles $\hat{I}{¸}_{\hat{I}¼e}$ and $\hat{I}{¸}_{ee}$, excluding part of the parameter space allowed by experimental anomalies. Cancellation of $\hat{I}{½}_e$ appearance and $\hat{I}{½}_e$ 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 paper and will be addressed by future analyses.

9 pages, 4 figures; supplemental: 6 pages, 8 figures