MicroBooNE

We present a measurement of the ν_e-interaction rate in the MicroBooNE detector that addresses the observed MiniBooNE anomalous low-energy excess (LEE). The approach taken isolates neutrino interactions consistent with the kinematics of charged-current quasi-elastic (CCQE) events. The topology of such signal events has a final state with 1 electron, 1 proton, and 0 mesons (1e1p). Multiple novel techniques are employed to identify a 1e1p final state, including particle identification that use two methods of deep-learning-based image identification, and event isolation using a boosted decision-tree ensemble trained to recognize two-body scattering kinematics. This analysis selects ν_e -candidate events in the reconstructed neutrino energy range of 200–1200 MeV, while 29.0 ± 1.9(sys) ± 5.4(stat) are predicted with ν_μ CCQE interactions used as a constraint. We use a simplified model to translate the MiniBooNE LEE observation into a prediction for a ν_e signal in MicroBooNE. A ∆χ² test statistic, based on the combined Neyman–Pearson χ² formalism, is used to define frequentist confidence intervals for the LEE signal strength. Using this technique, we exclude 0.25 (0.38) times the median MiniBooNE LEE signal strength at the 90% (2σ) confidence level. The expected upper limit under the assumption that there is no LEE signal is 0.75 (0.98) at the 90% (2σ) confidence level.