Primary cosmic-ray composition in the energy range of 1014 eV to 1016 eV and high-energy atmospheric cosmic rays observed with emulsion chambers at Mt. Kanbala

Summary  We report on the results of the measurements of energy spectra of atmospheric cosmic rays in the energy around 10 TeV measured with emulsion chambers at Mt. Kanbala (5500 m above sea-level, atmospheric depth 520 g/cm2). The power indices of the integral spectra take the values of 2.00±0.08 for gamma-rays and 1.90±0.10 for hadrons, in the energy range from 5 TeV to 20 TeV. Their intensities are compatible with those expected from the primary cosmic rays containing fewer protons than in the lower energy region. The energy spectrum of family events is also discussed with reference to the composition of primary cosmic rays. It is concluded that the portion of protons in the primary cosmic rays gradually decreases in the energy range from 1013 eV to 1015 eV.