A measurement of the cosmic ray muon charge ratio in the vertical direction and at 50°-90° East in the momentum range 3-20 Gev/c

Abstract

The cosmic-ray muon charge ratio at sea level has been examined in the momentum range 3-20 Gev/c in the vertical direction and at 50°-90 ° East. The measurements were made with a digitized Geiger counter hodoscope mounted on a solid-iron magnetic momentum spectrometer. This hodoscope was developed for this experimental study and provided automatic recording of muon trajectory information on magnetic tape. The recording of data in digitized computer compatible form allowed the analysis of approximately 100,000 muon events. A data analysis procedure was developed which provided more detailed information from the hodoscope data than could be derived by conventional procedures to date. Details of the experimental apparatus and the methods of data analysis are discussed. Muon charge ratios as small as 0.1 were observed at the largest zenith angles whereas the vertical charge ratios were near a constant value of 1.25. These experimental results are compared with the predictions of a muon production and propagation model which accounts for the geomagnetic deflection of muon trajectories. Due to the low range of momentum studied, the model predictions were carefully corrected for multiple coulomb scattering in the atmosphere.