Study of the primary spectrum and composition around the knee at the Andyrchy-BUST experiment

Abstract

The experimental data of the Andyrchy-BUST experiment are presented. The three types of experimental data, taken in our experiment, have been analyzed: high en- ergy muon number spectrum, EAS size spectrum and depen- dence of the mean number of high energy muons on EAS size. Joint analysis of these experimental data have been used for both studying the primary composition and testing inter- action models. In the range of primary energies of 10 14 10 15 eV per nu- cleus, direct methods for studying the energy spectrum and nuclear composition of primary cosmic rays become ineffi- cient because of a decrease in the flux of primary particles with an increase in their energy. Therefore, at these and, of course, higher energies, indirect methods based on simulta- neous measurement of the characteristics of different com- ponents of extensive air showers (EASs), initiated by the pri- mary particle in the atmosphere, are used. The interpretation of these measurements requires their comparison with EAS simulations in the atmosphere. In turn, the calculation re- sults depend on the hadronic interaction models. But it is widely known that none of the present interaction models can completely describe a full set of experimental data for cosmic rays. Joint analysis of the various characteristics of different EAS components measured in the same experiment can be used for both studying the primary composition and testing interaction models (Apel et al., 2007; Garyaka et al., 2008). At the Andyrchy-BUST experiment the electromag- netic and high energy muon components are measured. The electromagnetic component in our experiment is measured