Angular distribution of low-energy cosmic ray muons underground

Abstract

An experiment to study the angular distribution of stopping muons at a depth of 417 hg cm-2 (1 hg cm-2=100 g cm-2) at Kolar Gold Fields, India, has been completed. The best-fit value of the exponent, n, of the angular distribution is 2.23+or-0.33. From the observations it is concluded that the locally produced low-energy muons follow an angular distribution of the type I( theta ) varies as cos theta . On the basis of this conclusion the authors are able to interpret the abnormally high rate of low-energy muons relative to penetrating muons at a depth of 4270 hg cm-2 reported by Baschiera et al. (1971) as being due to a weighted combination of different exponents in the angular distribution of the atmospheric and locally produced components of stopping muons. They conclude that no unknown processes of low-energy muon production underground need be invoked to understand the observations.