First-principle event reconstruction by time-charge readouts for the Taishan Antineutrino Observatory

The Taishan Antineutrino Observatory (TAO) is a liquid-scintillator satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO) to measure the reference reactor neutrino spectrum with sub-percent energy resolution. We use inhomogeous Poisson process and Tweedie generalized linear model (GLM) to calibrate the detector response and the charge distribution of a SiPM. We develop a pure probabilistic method using time and charge of SiPMs from first principles to reconstruct point-like events in the TAO central detector. Thanks to our precise model and the high photo-coverage and quantum efficiency of the SiPM tiles at TAO, we achieve a vertex position resolution better than 16 mm and an energy resolution of about 2% at 1 MeV, marking the world's best performance of liquid scintillator detectors. Our methodology is applicable to other experiments that utilize PMTs for time and charge readouts.