Investigation of Muon Excess from Initial Hadronic Interactions in Cosmic Air Showers with a One-ton Scintillator Detector at CJPL

Over the past decade, ground-based array experiments have reported a notable deficit in simulated muons from extensive air showers (EAS) induced by high-energy cosmic rays, compared with experimental observations. This discrepancy is known as the \textit{muon puzzle}. In this work, we present the first study of this issue at the China Jinping Underground Laboratory (CJPL), where a 2400-m vertical rock overburden restricts muons to energies above 3 TeV, corresponding to an average primary cosmic-ray energy of about 0.4 PeV. This provides a clean window for probing the initial stages of EAS development. Using data collected over 1338.6 live days with the 1-ton prototype of the Jinping Neutrino Experiment, together with a GEANT4-based flux simulation framework, we perform a direct comparison between the measurement and predictions. Our results show that the observed muon flux is about 40% higher than post-LHC model expectations, offering new constraints for resolving the muon puzzle. These findings underscore the potential of deep underground environments for future high-energy cosmic-ray research.