Abstract
The existence of three distinct neutrino flavours, ν(e), ν(μ) and ν(τ), is a central tenet of the Standard Model of particle physics(1,2). Quantum-mechanical interference can allow a neutrino of one initial flavour to be detected sometime later as a different flavour, a process called neutrino oscillation. Several anomalous observations inconsistent with this three-flavour picture have motivated the hypothesis that an additional neutrino state exists, which does not interact directly with matter, termed as 'sterile' neutrino, ν(s) (refs. (3-9)). This includes anomalous observations from the Liquid Scintillator Neutrino Detector (LSND)(3) experiment and Mini-Booster Neutrino Experiment (MiniBooNE)(4,5), consistent with ν(μ) → ν(e) transitions at a distance inconsistent with the three-neutrino picture. Here we use data obtained from the MicroBooNE liquid-argon time projection chamber(10) in two accelerator neutrino beams to exclude the single light sterile neutrino interpretation of the LSND and MiniBooNE anomalies at the 95% confidence level (CL). Moreover, we rule out a notable portion of the parameter space that could explain the gallium anomaly(6-8). This is one of the first measurements to use two accelerator neutrino beams to break a degeneracy between ν(e) appearance and disappearance, which would otherwise weaken the sensitivity to the sterile neutrino hypothesis. We find no evidence for either ν(μ) → ν(e) flavour transitions or ν(e) disappearance that would indicate non-standard flavour oscillations. Our results indicate that previous anomalous observations consistent with ν(μ) → ν(e) transitions cannot be explained by introducing a single sterile neutrino state.