The physics of the knee in the energy spectrum of cosmic rays - air shower measurements with KASCADE

Jörg R. Hörandel für die KASCADE-Kollaboration
Universität Karlsruhe, Institut für Experimentelle Kernphysik, Hermann-von-Helmholtz-Platz 1, 76344 Leopoldshafen

The origin of high-energy cosmic ray particles, the processes of their propagation through the galaxy, and the origin of the knee in their energy spectrum are among the most interesting questions in particle astrophysics. The large multi-component air shower experiment KASCADE is operated since 1996 in order to address these issues. It measures the electromagnetic, muonic, and hadronic components of extensive air showers simultaneously in the energy range from below 1014 to above 1017 eV. Deriving conclusions of astrophysical relevance from air shower data needs a correct understanding of the cosmic-ray induced high-energy hadronic interactions in the atmosphere. Recent tests of hadronic interaction models used to describe the development of air showers in simulation codes such as CORSIKA are presented. Experimental access to the above mentioned astrophysical questions is provided through the measurement of the cosmic-ray mass composition, energy spectrum, and arrival directions. Actual results on the anisotropy of cosmic rays including a search for point sources will be discussed. A review of recent results, derived from different shower components, on the primary energy spectrum and the mass composition of cosmic rays is given and primary energy spectra for elemental groups will be presented.