Characterizing the energy resolution of the MicroBooNE LArTPC at the MeV scale using monoenergetic features of 208 Tl decays

A detailed understanding of the capabilities and fidelity of low-energy reconstruction is crucial for taking advantage of MeV-scale neutrino physics opportunities in liquid argon time projection chambers (LArTPCs). This study presents a measurement of the resolution of reconstructed energy in the MicroBooNE LArTPC at ≈ 1.5 MeV. The characterization is performed using monoenergetic signals generated by 2.614 MeV γ -rays from 208 Tl decays undergoing pair production in the detector. The resolution is found to be (7.52 ± 0.78 (stat)± 0.92 (syst))%. This value is consistent with the MicroBooNE simulation prediction of (9.70 ± 0.65 (stat))% at the 1.6 σ level. This study represents the first ever measurement of LArTPC energy resolution at the MeV scale and provides a pathway for monoenergetic energy calibrations in future experiments using LArTPC detectors.