Speaker
Description
The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kt liquid-
scintillator neutrino detector in China, ~53 km from two nuclear power plant complexes. It aims to determine the neutrino mass ordering and precisely measure neutrino oscillation parameters, while enabling studies on solar, atmospheric, geoneutrino, and supernova neutrino physics. The detector construction was completed, and physics data-taking began in August 2025.
Cosmic-ray muons dominate muon-induced backgrounds in JUNO by producing MeV-scale secondaries and radioactive spallation products, including neutrons, in the low-energy region. The surrounding PMT instrumented water-Cherenkov veto (water pool veto) provides efficient muon tagging, enabling the suppression of background and the characterization of performance. With limited high-energy calibration sources, accurate muon simulation is also essential for developing and validating high-energy event reconstruction, including direction and energy reconstruction in atmospheric neutrino analyses.
In this contribution, we present the current status and recent developments of the muon simulation in JUNO. We summarize the full workflow starting
from the mountain overburden model and the MUSIC-based propagation of cosmic muons through rock, followed by muon tracking within the detector volume using a customized Geant4-based detector simulation. We further cover downstream steps
relevant to water pool detector response studies, including the simulation of optical photon production and transport, trigger and electronics effects, and the reconstruction and analysis of muon events in the water pool.