Altitude profile of atmospheric muons in a location with relatively high cut-off rigidity

Abstract

We have investigated the differential and integrated muon fluxes, muon charge ratios and the zenith angle dependence of the integrated muon intensities at sea level and various depths in the atmosphere of Tsukuba, Japan, for muons with momenta below 400GeV/c using the Geant4 simulation package. The simulated sea level muon spectrum and charge ratio have been seen to be in good agreement, throughout the momentum interval of the interest, with those from the measurements made by the BESS-TeV spectrometer. Integrated muon intensities have been found to increase as the atmospheric depth decreases up to slightly above 200g/cm2, and then they have a trend to decrease at lower atmospheric depths. Muon charge ratios at each of the atmospheric depth of interest have been shown to have a very similar behavior with the one at sea level. Simulation results for the zenith angle dependence of muon intensity have been quite compatible with the existing information in the literature for sea level. It has also been shown that the zenith angular dependence of muon intensity has a tendency to disappear (to obey the secθ distribution) as the atmospheric depth decreases for muons with relatively low (high) momenta.