Study of hadronic component in air showers at Mt. Chacaltaya

An experiment of an air shower array, a hadron calorimeter (8 m2) and an emulsion chamber (8 m2, 15 cm Pb) is under way at Mt. Chacaltaya (5200 m above sea level, Bolivia), in order to study the hadron interactions and the primary cosmic rays in the energy region exceeding 1015 eV. The number of particles in the hadronic component in the air shower, which is detected by the hadron calorimeter, is not compatible with that obtained by simulations, indicating that violation of the Feynman scaling law is stronger at 1016 eV than the one assumed in the simulations. The average mass number of the primary cosmic rays, estimated from the distribution of the number of hadrons in the air shower, is < ln A >= 2.8 ± 0.5 at 1016 eV