Search for Neutrino-Induced Neutral Current $\hat{I}”$ Radiative Decay in MicroBooNE and a First Test of the MiniBooNE Low Energy Excess Under a Single-Photon Hypothesis

Abstract

We report results from a search for neutrino-induced neutral current (NC) resonant $\hat{I}”$(1232) baryon production followed by $\hat{I}”$ radiative decay, with a $⟨0.8⟩$~GeV neutrino beam. Data corresponding to MicroBooNE's first three years of operations (6.80$\times$10${}^{20}$ protons on target) are used to select single-photon events with one or zero protons and without charged leptons in the final state ($1\gamma 1p$ and $1\gamma 0p$, respectively). The background is constrained via an in-situ high-purity measurement of NC $\ddot{I}{€}^0$ events, made possible via dedicated $2\gamma 1p$ and $2\gamma 0p$ selections. A total of 16 and 153 events are observed for the $1\gamma 1p$ and $1\gamma 0p$ selections, respectively, compared to a constrained background prediction of $20.5\pm 3.65\text{(sys.)}$ and $145.1\pm 13.8\text{(sys.)}$ events. The data lead to a bound on an anomalous enhancement of the normalization of NC $\hat{I}”$ radiative decay of less than $2.3$ times the predicted nominal rate for this process at the 90% confidence level (CL). The measurement disfavors a candidate photon interpretation of the MiniBooNE low-energy excess as a factor of $3.18$ times the nominal NC $\hat{I}”$ radiative decay rate at the 94.8% CL, in favor of the nominal prediction, and represents a greater than $50$-fold improvement over the world's best limit on single-photon production in NC interactions in the sub-GeV neutrino energy range

7 pages, 7 figures, 4 tables. New version post-publication in PRL containing new plot