中国物理学会高能物理分会第十三届全国粒子物理学术会议（2021）

Solar-, geo-, and supernova neutrino experiments are subject to the background from cosmic-ray muons and muon-induced neutrons. China Jinping Underground Laboratory (CJPL), with its unique advantage of 2400 m rock coverage and far away from nuclear power plants, is ideal for neutrino search. Using a 1-ton prototype detector of the Jinping Neutrino Experiment, we detected 343 high-energy cosmic-ray muons and (6.24±3.66) muon-induced neutrons from an 820.28-day dataset at the first phase of CJPL (CJPL-I). The cosmic-ray muon flux is measured to be $ \rm (3.61\pm 0.19_{stat.}\pm 0.10_{sys.} )\times 10^{-10}\ cm^{-2}s^{-1} $ at CJPL-I, and the cosmic-ray muon flux of the second phase of CJPL (CJPL-II) is estimated to be $ \rm (2.3\sim 4.0)\times 10^{-10}\ cm^{-2}s^{-1} $ by Geant 4 simulation. The neutron yield in liquid scintillator is measured to be $ Y_{\rm LS}=(3.13\pm 1.84_{\rm stat.}\pm 0.67_{\rm sys.})\times 10^{-4}\ \mu^{-1}\rm g^{-1}cm^{2} $ with average muon energy at 340 GeV in CJPL-I, and estimated to be $ (3.4\sim 3.7)\times 10^{-4}\ \mu^{-1}\rm g^{-1}cm^{2} $ in CJPL-II. A global fit including this measurement shows a power-law coefficient of (0.75±0.02) for the dependence of the neutron yield at liquid scintillator on muon energy. The measurement of cosmogenic background in CJPL could serve as a basis for future large-scale detector development, like Jinping Neutrino Experiment, CDEX, and PandaX.