Investigation of muon lateral distributions and muon production heights in extensive air showers

The air shower experiment KASCADE is a groundbased detector system that measures simultaneously the electromagnetic, muonic and hadronic component. The Muon Tracking Detector registers muons with an energy threshold of 0.8 GeV in three horizontally arranged detector layers. It enables a detailed reconstruction of muon tracks as well of the angle components relative to the shower axis. The lateral distributions, determined by using tracks, are described analogous to the form of the electron lateral distribution (NKG-function). Measured distributions are compared to results of Monte Carlo simulations of proton and iron induced air showers. Used are the hadronic interaction models QGSJet and NEXUS that are implemented in CORSIKA. The muon densities determined with the Muon Tracking Detector have in average larger values than the ones of the Monte Carlo simulations. By comparing the form of the lateral distributions of measured data and Monte Carlo simulations one can determine the fractions of light and heavy particles of the primary cosmic rays. The muon production heights are calculated using the relative orientation of muon tracks to the shower direction. On the way through the atmosphere muons are hardly scattered because of little interactions. Thus the muons are used as probes of the longitudinal shower development. A re-calculation of the production heights using the atmospheric profile allows the investigation of the penetration depth of the primary cosmic rays. Analysis of the form of the muon lateral distributions, the mean radial angles and the mean production heights show a rise of the fraction of the heavy particles with increasing energy. (orig.)