Composition of primary cosmic rays above 1013 eV from the study of time distributions of energetic hadrons near air shower cores

Abstract

An experimental study of the distribution of arrival time of energetic hadrons relative to associated air shower particles has been made at a mountain altitude of 730 g.cm−2. Monte Carlo simulations of the expermental observations have shown that these observations are sensitive to the composition of primary cosmic rays of energies 1013–1015 eV. The energy spectra of primary protons and iron group nuclei required to understand these observations are (dN/dE)protons=1.5×104 E−2.71±0.06 m−2 sr−1 sec−1 Gev−1 (dN/dE)Fegroup=1.27 E−2.36±0.06 m−2 sr−2 sec−1 Gev−1 respectively, where E is energy per nucleon, indicating that iron group nuclei are the dominant component of primary cosmic rays at air shower energies of 1014–1016 eV.