Muon production in extensive air showers and fixed target accelerator data

One of the most promising approaches to determine the energy spectrum and composition of cosmic rays with energies above 1 PeV is the measurement of the number of electrons and muons produced in extensive air showers (EAS). Therefore EAS simulations using electromagnetic and hadronic interaction models are necessary. These simulations show uncertainties which are mainly related to hadronic interaction models. The aim of this thesis is to improve the reliability of EAS simulations by investigating the role of hadronic interactions for muon production. The importance of low energy interactions is studied and it is argued that current fixed target experiments can help to reduce uncertainties in the low energy range. This is demonstrated by analyzing data of the CERN fixed target experiment HARP on proton and pion interactions with a carbon target and by comparing the obtained production spectra with model predictions. The simulation studies of the relevant energies and phase space regions of hadronic interactions in EAS form the basis on the cosmic ray part of a proposal for a new fixed target experiment. Early 2007 the proposal was accepted by CERN and the new NA61 experiment will take first p+C data at 30 GeV in autumn of 2007.