Inclusive Search for Anomalous Single-Photon Production in MicroBooNE

TL;DR

This paper reports a search for anomalous single-photon events in MicroBooNE, motivated by previous excesses, using a new reconstruction framework and background constraints, finding no significant excess overall.

Contribution

It introduces an inclusive single-photon search in MicroBooNE with improved background control and reports results consistent with background predictions.

Findings

Data agrees with background prediction in the full signal region.

A sub-sample shows a slight excess of events above prediction at low energies.

No significant evidence for anomalous single-photon production was observed.

Abstract

We present an inclusive search for anomalous production of single-photon events from neutrino interactions in the MicroBooNE experiment. The search and its signal definition are motivated by the previous observation of a low-energy excess of electromagnetic shower events from the MiniBooNE experiment. We use the Wire-Cell reconstruction framework to select a sample of inclusive single-photon final-state interactions with a final efficiency and purity of 7.0% and 40.2%, respectively. We leverage simultaneous measurements of sidebands of charged current $\nu_{\mu}$ interactions and neutral current interactions producing $\pi^{0}$ mesons to constrain signal and background predictions and reduce uncertainties. We perform a blind analysis using a dataset collected from February 2016 to July 2018, corresponding to an exposure of $6.34\times10^{20}$ protons on target from the Booster Neutrino Beam (BNB) at Fermilab. In the full signal region, we observe agreement between the data and the prediction, with a goodness-of-fit $p$-value of 0.11. We then isolate a sub-sample of these events containing no visible protons, and observe $93\pm22\text{(stat.)}\pm35\text{(syst.)}$ data events above prediction, corresponding to just above $2\sigma$ local significance, concentrated at shower energies below 600 MeV.