Measurement of Cosmic Ray Flux in China JinPing underground Laboratory

TL;DR

This paper reports the measurement of cosmic ray muon flux in China JinPing underground Laboratory, demonstrating its ultra-low background environment suitable for dark matter research.

Contribution

It provides the first precise measurement of cosmic ray flux in CJPL, confirming its suitability for rare event physics experiments.

Findings

Cosmic ray muon flux in CJPL is (2.0±0.4)×10^(-10) /cm^2/s.

CJPL has an ultra-low cosmic ray background.

The measurement supports CJPL's use for dark matter experiments.

Abstract

China JinPing underground Laboratory (CJPL) is the deepest underground laboratory presently running in the world. In such a deep underground laboratory, the cosmic ray flux is a very important and necessary parameter for rare event experiments. A plastic scintillator telescope system has been set up to measure the cosmic ray flux. The performance of the telescope system has been studied using the cosmic ray on the ground laboratory near CJPL. Based on the underground experimental data taken from November 2010 to December 2011 in CJPL, which has effective live time of 171 days, the cosmic ray muon flux in CJPL is measured to be (2.0+-0.4)*10^(-10)/(cm^2)/(s). The ultra-low cosmic ray background guarantees CJPL's ideal environment for dark matter experiment.