A study of high energy muons and neutrinos underground

Abstract

The results are presented of an investigation into the flux of cosmic ray muons underground at a depth of 7500 m.w.e. in the Kolar Gold Fields, South India. Muons from the decay of pions produced in the first high energy interactions of energetic cosmic rays in the upper atmosphere were observed to arrive from directions close to the vertical. The angular distribution, depth-intensity relation and electromagnetic interaction products of the muons are discussed and conclusions are drawn about the behaviour of these characteristics at very great depths. An examination is made of the way in which muons loose energy in various media and from this study the range-energy relations for muons in standard rock and sea water are constructed. A comparison of recent underwater and underground measurements at depths down to I5OO m.w.e, is made and it is shown that the sea level energy spectra derived from measurements under the two types of media are nearly identical and close to the spectrum given by Osborne et al. (1964).At angles close to the horizontal, muons were detected in the underground laboratory from the interactions of neutrinos with nucleons in the surrounding rock wall. Definite evidence was obtained, by means of a visual neon flash tube technique, that the neutrino interactions are mainly non-elastic in character, and that the rate of muons observed agrees well with theory, though on the presently available statistics it is not possible to decide whether or not the role played by the theoretically predicated intermediate boson is significant. The results comparable experiments re presented and the future development and aims of the Kolar Gold Fields experiment discussed.