Muon Tracking with the fastest light in the JUNO Central Detector

TL;DR

This paper presents a muon tracking algorithm for the JUNO detector that uses the earliest light detected by photomultiplier tubes to accurately reconstruct muon trajectories, aiding background rejection.

Contribution

The paper introduces a novel muon tracking method based on the first hit time correction and least squares fitting, achieving high spatial and angular resolution in JUNO.

Findings

Spatial resolution better than 3 cm

Angular resolution better than 0.4 degrees

Tracking efficiency exceeds 90% up to 16 m from the center

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment designed to measure the neutrino mass hierarchy using a central detector (CD), which contains 20 kton liquid scintillator (LS) surrounded by about 18,000 photomultiplier tubes (PMTs), located 700~m underground. The rate of cosmic muons reaching the JUNO detector is about 3~Hz and the muon induced neutrons and isotopes are major backgrounds for the neutrino detection. Reconstruction of the muon trajectory in the detector is crucial for the study and rejection of those backgrounds. This paper will introduce the muon tracking algorithm in the JUNO CD, with a least squares method of PMTs' first hit time (FHT). Correction of the FHT for each PMT was found to be important to reduce the reconstruction bias. The spatial resolution and angular resolution are better than 3~cm and 0.4~degree, respectively, and the tracking efficiency is greater than 90\% up to 16~m far from the detector center.