Application of the timing and charge based on muon track reconstruction algorithm for water Cherenkov detector

BackgroundThe reconstruction of cosmic ray tracks is highly important in large neutrino detectors. Precise track reconstruction can effectively eliminate isotopic backgrounds around the tracks without requiring anti-coincidence measures across the entire detector. The muon reconstruction in the water buffer region (interlayer water) of the Central Detector (CD) has not been studied, which is called CD Water Buffer (CWB) muon. The CWB muon event number is about 20% of the muons that pass through the CD.PurposeThis study aims to develop a new reconstruction method for muon tracks and measure the mass ordering of neutrinos based on the background, veto strategy and effective volume cut.MethodsThe earliest photon arrival time and charge information from the photomultiplier tube signals was ultilized to construct a charge-weighted least squares time equation. Then, this method was successfully applied to large water Cherenkov detectors through simulation studies and parameter adjustments. Finally, the JUNO (Jiangmen Underground Neutrino Experiment) Cherenkov detector was taken as a case study, and Geant4 simulations were performed to optimize parameters.ResultsSimulation results show that muon track reconstruction in the water layer is achieved with a spatial resolution better than 12 cm, an angular resolution better than 0.4°, and a reconstruction efficiency of approximately 97%.ConclusionsThese results demonstrate that muon track reconstruction proposed in this study can help JUNO to further reduce the background, which plays an important role in the sensitivity analysis of JUNO in the future.