Calculation of Muon Fluxes at the Small Atmospheric Depths

Precise knowledge of the hadronic interaction between primary cosmic rays and atmospheric nuclei is very important and fundamental to study atmospheric neutrinos and their oscillations. We studied hadronic interaction models using the data of primary and secondary cosmic rays observed by BESS experiments. By comparing the observed spectra with the ones calculated by several interaction models, we found DPMJET-III is most favored among them.