Investigation of the zenith angle dependence of cosmic-ray muons at sea level

Abstract

Angular distribution of cosmic-ray muons at sea level has been investigated using the Geant4 simulation package. The model used in the simulations was tested by comparing the simulation results with the measurements made using the Berkeley Lab cosmic ray detector. Primary particles' energy and fluxes were obtained from the experimental measurements. Simulations were run at each zenith angle starting from theta = 0A degrees up to theta = 70A degrees with 5A degrees increment. The angular distribution of muons at sea level has been estimated to be in the form I(theta) = I(0A degrees) cos (n) (theta), where I(0A degrees) is the muon intensity at 0A degrees and n is a function of the muon momentum. The exponent n = 1.95 +/- 0.08 for muons with energies above 1 GeV is in good agreement, within error, with the values reported in the literature.