Search for an Anomalous Excess of Single Photons in the MicroBooNE Neutrino Experiment

TL;DR

This paper reports a search for an excess of single photon events in the MicroBooNE experiment to investigate unexplained anomalies observed in previous neutrino experiments, aiming to clarify their origin.

Contribution

It introduces a novel analysis targeting neutral current Delta radiative decays to identify potential sources of single photon excesses in MicroBooNE data.

Findings

Data is consistent with expectations, showing no significant excess.

Cannot exclude some sources of photon events without visible proton activity.

Highlights the potential for further detailed studies in future experiments.

Abstract

Neutrinos are some of the most elusive particles in the standard model, being incredibly common throughout the universe, but interacting with detectors incredibly rarely. Certain properties of neutrinos remain difficult to measure, including their masses, their CP violation properties, and whether or not they are their own antiparticles. Additionally, there have been several anomalous results in neutrino experiments which remain unexplained. MicroBooNE was built in order to study these anomalous results using a more capable detector technology, the Liquid Argon Time Projection Chamber. Specifically, MicroBooNE is able to search for an anomalous excess of low energy electromagnetic showers, which was previously observed by the MiniBooNE experiment. In particular, MicroBooNE is able to study whether the excess could consist of electron showers or photon showers. In this thesis, I describe a search for this anomalous excess by targeting neutral current Delta radiative decays, the largest expected source of single photons in MicroBooNE. We observe data consistent with our nominal expectation, but cannot rule out all potential sources of additional single photon events, particularly those with no visible proton activity. There remains significant potential to probe this channel in even more detail using MicroBooNE and other experiments in the near future.