Study of neutron production for 360 GeV cosmic muons

TL;DR

This study measures the neutron production by high-energy cosmic muons at the CJPL, providing detailed data on muon flux and neutron yield in a deep underground environment, relevant for neutrino experiments.

Contribution

It presents the first detailed analysis of muon-induced neutron production at ~360 GeV in a deep underground laboratory, including effects of detector size on measurements.

Findings

Muon flux measured as (3.56±0.16_stat±0.10_syst)×10^{-10} cm^{-2}s^{-1}

Cosmogenic neutron yield determined as (3.37±1.41_stat±0.31_syst)×10^{-4} μ^{-1} g^{-1} cm^{2}

Analysis of secondary particle leakage effects on neutron yield measurement

Abstract

The China Jinping underground Laboratory (CJPL) is an excellent location for studying solar, terrestrial, and supernova neutrinos due to its 2400-meter vertical rock overburden. Its unparalleled depth gives an opportunity to investigate the cosmic-ray muons with exceptionally high average energy at $\sim360$ GeV. This paper details a study of muon-related backgrounds based on 1178 days of data collected by the 1-ton prototype neutrino detector used for the Jinping Neutrino Experiment (JNE) since 2017. The apparent effects for the leakage of muons' secondary particles due to detector's finite size on the measured neutron yield are first discussed in detail. The analysis of 493 cosmic-ray muon candidates and $13.6\pm5.7$ cosmogenic neutron candidates, along with a thorough evaluation of detection efficiency and uncertainties, gives a muon flux of $(3.56\pm0.16_{\mathrm{stat.}}\pm0.10_{\mathrm{syst.}})\times10^{-10}~\mathrm{cm}^{-2}\mathrm{s^{-1}}$ and a cosmogenic neutron yield of $(3.37\pm 1.41_{\mathrm{stat.}}\pm 0.31_{\mathrm{syst.}}) \times 10^{-4}~\mathrm{\mu}^{-1} \mathrm{g}^{-1} \mathrm{cm}^{2}$ in LAB-based liquid scintillator.