First constraints on light sterile neutrino oscillations from combined appearance and disappearance searches with the MicroBooNE detector

Blake, A. and Devitt, A. and Nowak, J. and Patel, N. and Pophale, I. and Thorpe, C. (2023) First constraints on light sterile neutrino oscillations from combined appearance and disappearance searches with the MicroBooNE detector. Physical review letters, 130 (1): 011801. ISSN 1079-7114

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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 $\nu_e$ and $\nu_{\mu}$ 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 $\Delta m^2_{41}$ 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 $3+1$ 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.