Muon-Pair Separation Measurements and Comparison with Transverse-Momentum Models

Rates of high-energy cosmic-ray muon pairs have been measured for separations up to 70 m. Detailed calculations imply that the mean transverse momentum 〈pT〉 of mesons with $x>0.01$ is 0.66 ±{} 0.10 GeV/c at laboratory energies of {} 10 000 GeV. We find that the high-pT muons result mostly from decay of abundantly produced particles with lifetimes {} 10^-8 sec, such as pions and kaons.