Cosmic ray data on high-energy hadron-nucleus and nucleus-nucleus collisions

This lecture concentrates on two aspects of what is known from cosmic rays about nucleus-nucleus interactions: what part of cosmic ray physics immediately would benefit from having a 20-GeV per nucleon machine colliding with 20 GeV per nucleon and how it might be relevant to some cosmic ray questions, and the unusual cosmic ray events called Centauro events. The origin, acceleration, and propagation of cosmic rays are touched upon, with a description of the leaky box model. A typical cosmic ray experiment and its data analysis are described. Then the Centauro events are discussed. The most significant point is that the number of associated gamma rays and electrons is very small, while the total number of hadrons is of the order of 100; these events have no accepted explanation. 16 figures, 4 tables