Absolute intensities of energetic cosmic ray muons near sea level

The absolute intensities of cosmic ray muons in the vertical direction and at several large zenith angles in the geomagnetic west have been measured for momenta in the range 3-100 GeV/c by use of a solid-iron magnetic momentum spectrometer-telescope. Details of the experimental apparatus are presented, and the methods of measurement and analysis of the basic data from photographic re-projection of film records of events in wide-gap spark chambers are discussed. The intensities of the present experiment are systematically ~15-40% higher than previously reported intensities at comparable momenta and zenith angles. Reasons for believing that the present work is of improved accuracy in comparison with previous experimental work and actually gives absolute intensities are presented. The impact of these results on several areas of high-energy nuclear and cosmic ray physics is discussed