Coupling constants for the cosmic ray muon component

An apparatus employing twin telescopes to study the azimuthal variation of cosmic ray muon intensity was operated at Ahmedabad (geographic 23 degrees N, 37 degrees E; geomagnetic latitude 14 degrees N). Fourteen directions were scanned for long time intervals to give a counting rate accuracy of about 0.4% for each direction. Experimental results are presented. Variation in the coupling constant values in the rigidity range 12-26 GV is rather flat. Some implications of this behaviour are discussed. A theoretical method is described for the estimation of coupling constants applicable to muon telescopes. Correction for the fact that alpha particles and heavy particles have a cut-off (in terms of momentum per nucleon) at half the value for protons is incorporated in the calculation. The method is verified by comparing the theoretical results with experimental data on the latitude effect (namely, for zenith direction) and on the azimuth effect for fixed zenith angles. Theoretically estimated coupling constants for different zenith angles and different atmospheric depths are presented.