The absolute depth-intensity curve for cosmic-ray muons underwater and the integral sea-level momentum spectrum in the range 1-100 GeV/c

Abstract

A portable scintillation counter telescope has been used to measure the absolute intensities of cosmic-ray muons underwater at 11 depths in the range 10-175 m. Over this depth range the depth-intensity curve is found to be well represented by the Miyake relationship I=A0h- alpha e- beta h/(h+h1) with A0, alpha , beta and h1 being 29.5, 1.32, 1.6*10-3 and 123.0, respectively. Using a calculated range-energy relationship for muons in water, the integral sea-level momentum spectrum was obtained from the depth-intensity curve for the momentum range 1-100 GeV/c. This spectrum has been compared with spectra reported by workers using both magnet and range spectrographs, and it is found that the present spectrum differs from these in both the absolute intensity values (intensity at >1 GeV/c=(6.29+or-0.40)*10-3 cm-2 s-1 sr-1 compared with 7.22*10-3 cm-2 s-1 sr-1 quoted by Allkofer et al.) and in the spectral shape. It is concluded that the differences result from the use of a simple muon propagation model to derive spectra from spectrograph data since this model leads to a distorted spectrum.