The interactions of cosmic ray neutrinos

A collaboration experiment between i'ata Institute, Bombay, Osaka City University and Durham University has been performed underground at a depth of 7500 m.w.e. in Kolar Gold Fields, South India, primarily to study muons produced by the interactions of cosmic ray neutrinos. The results obtained are described and analysed. The rate of neutrino-induced muons has been found to be less than predicted for several widely different assumptions made about the inelastic interaction cross section above 10 G-eV (the limit of the machine data). However the results clearly show the importance of the inelastic interaction and suggest that the cross section continues to rise to ɝ 30 G-eV/c whilst the fraction of energy taken by the muon falls. The energies of two neutrino-induced muons have been measured with magnetic spectrographs and neutrino interactions inside the detectors have been recorded along with unambiguous examples of upv/ard moving muons. Muons of atmospheric origin have also been detected and both their intensity and angular distribution have been established and described by appropriate expressions. Their energy spectra and meajn energies have been predicted and compared with those derived from observations made of their electromagnetic accompaniment. The celestial co-ordinates of the arrival directions of neutrino- induced muons may be suggestive of a possible point source of extra-terrestrial neutrinos and these of the atmospheric muons have shown a possible large scale anisotropy in the southern celestial hemisphere, the implications of which are discussed. These results are compared with those of other workers and the future plans for cosmic ray neutrino studies are discussed.