The Energy Spectrum and the Chemical Composition of primary Cosmic Rays with Energies from 10~(14) to 10~(16) eV

摘要

We have measured extensive air showers(EASs) with primary energies above 6 TeV at Mt.Chacaltaya in Bolivia since March 2000 with an air shower array called the Minimum Air Shower(MAS) array.With an equi-intensity method analysis,we obtained longitudinal development curves of EAS around and deeper than their maximum developments to be compared with simulations,in which the primary chemical composition is assumed to be a mixture of protons and irons.We determined the mixing ratio of protons as a function of the primary energy,and we derived the primary energy spectrum from 10~(14) to 5 x 10~(16) eV.We found that the average mass number of primary cosmic rays increase with energy above 10~(14.5) eV and the dominant component around the knee is not protons.