Scintillation light calibrations, systematic uncertainties, and triggering efficiency in the MicroBooNE detector

TL;DR

This paper details the calibration, systematic uncertainties, and efficiency of scintillation light detection in the MicroBooNE LArTPC, including long-term stability, noise issues, and implications for rare-event searches.

Contribution

It provides a comprehensive analysis of light detection performance, calibration procedures, and introduces new observations on light yield decline and noise rates over five years.

Findings

50% decline in light yield over two years

Higher than expected single photoelectron noise rate (~200 kHz)

Benchmarking of long-term light detection stability in LArTPCs

Abstract

Scintillation light, produced alongside ionisation charge from particle interactions, plays a critical role in liquid argon time projection chamber (LArTPC) detectors. A detailed understanding of its production and detection mechanisms is essential for robust calibration, systematic uncertainty evaluation, and physics analysis. This article describes the MicroBooNE light simulation, light-based triggering schemes, photomultiplier tube gain calibration, light response stability, and light-based systematic uncertainties over the course of five years of data collection. In addition, we present a measurement of scintillation light triggering efficiency, focusing on the lowest-light regime relevant to rare-event searches and low-energy neutrino interactions. Finally, we discuss two notable observations in MicroBooNE's data, both reported here for the first time: an approximately 50% decline in MicroBooNE's light yield over time, concentrated in the first two years of running; and a higher than expected O(200 kHz) rate of single photoelectron noise. The results presented provide an important benchmark of long-term light detection performance in LArTPC neutrino detectors.