Measurement of Cosmic-ray Muons and Muon-induced Neutrons in the Aberdeen Tunnel Underground Laboratory

Abstract

We have measured the muon flux and production rate of muon-induced neutrons at a depth of 611 m water equivalent. Our apparatus comprises three layers of crossed plastic scintillator hodoscopes for tracking the incident cosmic-ray muons and 760 L of gadolinium-doped liquid scintillator for producing and detecting neutrons. The vertical muon intensity was measured to be $I_{\hat{I}}¼=(5.7\pm 0.6)\times 10^{-6}$ cm${}^{-2}$s${}^{-1}$sr${}^{-1}$. The yield of muon-induced neutrons in the liquid scintillator was determined to be $Y_n=(1.19\pm 0.08(stat)\pm 0.21(syst))\times 10^{-4}$ neutrons/($\hat{I}¼\cdot$g$\cdot$cm${}^{-2}$). A fit to the recently measured neutron yields at different depths gave a mean muon energy dependence of ${⟨E_{\hat{I}}¼⟩}^{0.76\pm 0.03}$ for liquid-scintillator targets.

14 pages, 17 figures, 3 tables