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 a gadolinium-doped liquid scintillator for producing and detecting neutrons. The vertical muon intensity was measured to be I-mu = (5.7 +/- 0.6) x 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 +/- 0.08(stat) +/- 0.21(syst)) x 10(-4) neutrons/(mu.g.cm(-2)). A fit to the recently measured neutron yields at different depths gave a mean muon energy dependence of < E-mu >(0.76 +/- 0.03) for liquid-scintillator targets.