Neutron Source-Based Event Reconstruction in the JUNO Detector

The Jiangmen Underground Neutrino Observatory (JUNO) is the world's largest underground liquid scintillator experiment, under construction in South China. The primary goal of this experiment is to determine the neutrino mass ordering with the energy spectrum from the reactor anti-electron neutrinos. The JUNO detector consists of a 20-kton liquid scintillator in an acrylic vessel which is viewed by 17,612 20-inch photomultiplier tubes (PMTs) and 25,600 3-inch PMTs. The key component for determining the neutrino mass ordering is to reach a similar to 3% energy resolution at 1 MeV for reactor neutrino events and to understand the non-uniform response of the detector. This proceedings paper describes vertex and energy reconstruction algorithms in the JUNO detector, which have been developed based on neutron source and laser calibration events. Using the JUNO detector simulation, the vertex reconstruction bias has been estimated to be within 4 cm, and the resolution for positrons with E-kin = 0 MeV has been evaluated to be about 9 cm. As for the energy reconstruction performance, the non-uniform bias has been estimated to be less than 0.5%.