The muon charge ratio at sea level

The energy dependence of the charge ratio of cosmic ray muons at sea level has been calculated. Pion production by pions, kaon production by kaons and kaon production by pions have been included. Approach to scaling has been assumed and determined from accelerator data for π+, π-, K+, K-, p and n production by nucleons. The charge ratio is found first to decrease with increasing energy up to about 50 GeV because of the approach to scaling. Then the change of the spectral exponent γ from 1.70 to 1.60 causes the charge ratio to drop by about 0.02 at about 50 GeV (at zenith angle theta = 750). This is also clearly seen from experiments. Above 100 GeV the muon charge ratio increases with energy because muons from decay of kaons become more important. It is not necessary to assume any 'abnormal' composition of the primary spectra (n/p ratio) at high energies where direct measurements are not possible to account for the muon charge ratio. (Auth.)