Cosmic-Ray Muon Intensity Deep Underground versus Depth

Abstract

Cosmic-ray muons produced in the earth's atmosphere were measured at a depth of 8.71×${10}^5$ g ${\mathrm{cm}}^{-2\mathrm{}}$ with a large-area (170 ${\mathrm{m}}^2$) liquid-scintillation-detector hodoscope. These data taken together with those of other workers lead to an improved muon vertical-depth intensity curve, $I_v\mathrm{}\left(h\right)=a_{\mu }{e}^{-\frac{h}{\lambda }}$, where $I_v\mathrm{}\left(h\right)=\mathrm{vertical}\mathrm{intensity}$, $a_{\mu }=\left({{1.04}_{-0.13\mathrm{}}}^{+0.21\mathrm{}}\right)\times {10}^{-6\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$, $\lambda =\left({{8.04}_{-0.39\mathrm{}}}^{+0.35\mathrm{}}\right)\times {10}^4$ g ${\mathrm{cm}}^{-2\mathrm{}}$, and $h=\mathrm{depth}$ in g ${\mathrm{cm}}^{-2\mathrm{}}$. A comparison of these results with those expected from the sea-level muon spectra via an improved calculation may indicate the need for an increased energy loss, probably via the photonuclear interaction as suggested by Keuffel et al. The results are not inconsistent with the presence of the $X$ process of Keuffel et al.