A measurement of the cosmic-ray primary composition between 3 X 10 to the 13th and 3 X 10 to the 15th eV using underground muons

The multiplicities of high-energy muons (E(mu) greater than 2.6 TeV) detected deep underground by the Homestake liquid scintillation hodoscope are examined for sensitivity to the cosmic-ray primary composition in the energy range from 3 x 10 to the 13th to 3 x 10 to the 15th eV. Using a two-component (proton and iron) energy-independent composition model, it is found that the best primary composition model contains 83 + or - 13 percent protons and 17 percent iron. Using an energy-dependent five-component model, it is found that the multiple muon rates are in good agreement (67.4 chi sq probability) with a proton-dominated primary composition, as suggested by Fichtel and Linsley (1986). An iron-enriched primary composition does not provide a good fit to the experimental data (0.38 percent chi sq probability).