China Jinping Underground Laboratory (CJPL) is ideal for studying solar-, geo-, and supernova neutrinos. A precise measurement of the cosmic-ray background would play an essential role in proceeding with the R\&D research for these MeV-scale neutrino experiments. Using a 1-ton prototype detector for the Jinping Neutrino Experiment (JNE), we detected 264 high-energy muon events from a 645.2-day dataset at the first phase of CJPL (CJPL-I), reconstructed their directions, and measured the cosmic-ray muon flux to be (3.53±0.22stat.±0.07sys.)×10−10 cm−2s−1. The observed angular distributions indicate the leakage of cosmic-ray muon background and agree with the simulation accounting for Jinping mountain's terrain. A survey of muon fluxes at different laboratory locations situated under mountains and below mine shaft indicated that the former is generally a factor of (4±2) larger than the latter with the same vertical overburden. This study provides a convenient back-of-the-envelope estimation for muon flux of an underground experiment.
@article{arxiv.2007.15925,
title = {Muon Flux Measurement at China Jinping Underground Laboratory},
author = {Ziyi Guo and Lars Bathe-Peters and Shaomin Chen and Mourad Chouaki and Wei Dou and Lei Guo and Ghulam Hussain and Jinjing Li and Qian Liu and Guang Luo and Wentai Luo and Ming Qi and Wenhui Shao and Jian Tang and Linyan Wan and Zhe Wang and Benda Xu and Tong Xu and Weiran Xu and Yuzi Yang and Minfang Yeh and Lin Zhao},
journal= {arXiv preprint arXiv:2007.15925},
year = {2021}
}