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

TL;DR

This paper presents a first-principles probabilistic model for event reconstruction in the TAO neutrino detector, achieving unprecedented spatial and energy resolution by modeling SiPM responses with inhomogeneous Poisson processes and Tweedie GLMs.

Contribution

The authors develop a novel probabilistic approach based on first principles to accurately reconstruct events in liquid scintillator detectors using time and charge readouts.

Findings

Vertex resolution better than 20mm

Energy resolution of about 2% at 1MeV

Achieved world's best performance for liquid scintillator detectors

Abstract

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 unprecented energy resolution. We use inhomogeous Poisson process and Tweedie generalized linear model (GLM) to characterize the detector response and the charge distribution of a SiPM. We develop a pure probabilistic model for 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 vertex position resolution better than 20mm, energy resolution of about 2% at 1MeV and <0.5% non-uniformity, marking the world's best performance of liquid scintillator detectors. With such resolution, we perceive MeV events to exhibit track effects. It opens up an exciting possibility of computed tracking calorimeter for unsegmented liquid scintillator detector like TAO. Our methodology is applicable to other experiments that utilize PMTs for time and charge readouts.