Search

This thesis reports a search for anomalous production of inclusive single photon events from neutrino interactions using the Wire-Cell event reconstruction package in the MicroBooNE experiment, which is motivated by the previous observation of a low-energy excess (LEE) of electromagnetic events from the MiniBooNE experiment. In the last few decades, multiple short-baseline experiments have reported anomalies in their measurements of neutrino interactions. Among them is the MiniBooNE experiment, which has reported a 4.8$\sigma$ excess of single electromagnetic shower events in the low energy region ($E_\nu \sim$100--800 MeV), commonly referred to as the MiniBooNE Low-Energy Excess (LEE)\cite{mb:2021}. However, the nature of these events remains unknown due to MiniBooNE's inability to distinguish between electron- and photon-induced showers. The Short-Baseline Neutrino (SBN) Program at Fermilab aims to shine light on the nature and origin of the MiniBooNE anomaly.Running from 2015 to 2021, MicroBooNE was the first SBN detector to collect data and has already begun to probe the MiniBooNE anomaly. In MicroBooNE's first round of LEE results, which consisted of both electron-like and photon-like excess searches, no significant excess was seen in events with a single electron-like or single photon-like electromagnetic shower in the final state~\cite{uB_eLEE_PRL,uB_gLEE}. However, unlike the electron-like LEE searches, which covered a wide range of final states and possible processes, the photon-like LEE search only focused on one specific model, that of \ncdeltaNgamma{} decays. Given these results, a more general search for photon-like events was needed to complete a model-independent investigation of the MiniBooNE anomaly. This thesis describes such a model-independent analysis searching for events from neutrino interactions that result in a single photon, above 20 MeV kinetic energy, inside the MicroBooNE detector volume, with no charged leptons and any number of hadrons. A selection of inclusive single photon final-state interactions using the Wire-Cell event reconstruction package, with a final selection efficiency of 7.0\% and purity of 40.2\%, is described. Systematic uncertainties and statistical treatments are also discussed. Sidebands to provide measurements of \numuCC{} and \ncpio{} interactions are created and used to constrain signal and background predictions and reduce uncertainties for the rare single photon interactions. A blind analysis was performed using a data set collected from Feb 2016 to July 2018, corresponding to an exposure of 6.34$\times$10$^{20}$ protons on target from the Booster Neutrino Beam (BNB) at FNAL. In the full signal region, we observe an excess of single-photon events with a significance of less than 2.0$\sigma$. In a subsample of these events containing no observed protons, we observe an excess of $92.8$ events above prediction, corresponding to a 2.0$\sigma$ significance, concentrated mostly in shower energies below 600 MeV. Additionally, the final detector of the SBN program, SBND, is planned to begin physics data-taking in 2024. It expects to acquire orders of magnitude more neutrino data that can be used for future expansions of this investigation. Work on the commissioning of SBND is presented.