Muon-pair production by cosmic-ray muons

Thirty-three examples of muon pair production by muons were observed in a large cosmic-ray detector comprised of cylindrical spark counters and water Cerenkov counters having an automatic digitized data-handling system. These events were found in the analysis of 2 060 000 incident cosmic-ray muon trajectories recorded for study during 837 hours of running time between March and August 1966. Backgrounds from all sources contribute, at most, three events to this sample. The measured cross-section agrees qualitatively with the theory of Murotaet al. Experimental uncertainties prevent a more accurate comparison of theory and experiment.