Measurement of Muon-induced Neutron Production at the China Jinping Underground Laboratory

TL;DR

This study measures muon-induced neutron production at CJPL, providing first data on neutron backgrounds relevant for neutrino experiments and establishing a power-law relationship with muon energy.

Contribution

The paper presents the first measurement of muon-induced neutron yield at CJPL and characterizes its dependence on muon energy.

Findings

Muon-induced neutron yield measured as (3.44 ± 1.86_stat ± 0.76_syst)×10^{-4} μ^{-1} g^{-1} cm^2.

Detected 343 high-energy muons and 7.86 ± 3.97 muon-induced neutrons over 820 days.

Power-law coefficient of neutron yield dependence on muon energy is 0.75 ± 0.02.

Abstract

Solar, terrestrial, and supernova neutrino experiments are subject to muon-induced radioactive backgrounds. The China Jinping Underground Laboratory (CJPL), with its unique advantage of a 2400 m rock coverage and long distance from nuclear power plants, is ideal for MeV-scale neutrino experiments. Using a 1-ton prototype detector of the Jinping Neutrino Experiment (JNE), we detected 343 high-energy cosmic-ray muons and (7.86$ \pm $3.97) muon-induced neutrons from an 820.28-day dataset at the first phase of CJPL (CJPL-I). Based on the muon-induced neutrons, we measured the corresponding muon-induced neutron yield in a liquid scintillator to be $ (3.44 \pm 1.86_{\rm stat.}\pm 0.76_{\rm syst.})\times 10^{-4}\mu ^{-1}\rm g^{-1}cm^{2} $ at an average muon energy of \SI{340}{GeV}. We provided the first study for such neutron background at CJPL. A global fit including this measurement shows a power-law coefficient of (0.75$ \pm $0.02) for the dependence of the neutron yield at the liquid scintillator on muon energy.