Heavy ion interactions in nuclear emulsions induced by 2 GeV/nucleon 16O have been studied. The reaction cross sections determined are 337-85 +56 mb, 1007-174 +175 mb and 2180-231 +304 mb for interactions with H, CNO and AgBr, respectively. Energy-, angular- and transverse momentum distributions of non-relativistic protons (E400 MeV) and all He nuclei have been analysed. Statistical models assuming small correlations among nucleon momenta can account for the main part of the He emission. The energy- and transverse momentum distributions of protons, emitted from light as well as heavy target nuclei indicate that intranuclear nucleon-nucleon scattering is the most important proton emission process. The angular distributions of both high energy protons and high energy He nuclei emitted from the target nucleus differ considerably in central and peripheral 16O-AgBr interactions. In order to explain the angular distributions of high energy protons and He nuclei in events with extremely small impact parameter, non-statistical phenomena, possibly hydrodynamic shock wave emission, must be considered.

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Nucleus-nucleus collisions produced in nuclear emulsions by heavy cosmic ray primaries have been analysed. The kinetic energy of the incident nuclei are larger than 100 MeV/nucleon. The angular and energy distributions of protons with energies <10 MeV and alpha-particles with energies <200 MeV have been studied. Low energy protons and alpha-particles are emitted isotropically in a system moving with a mean velocity component in the forward direction of 0.02 c. It is found that there is an excess of low energy protons which cannot be explained without using extremely low values of the Coulomb barrier. It is also found that evaporation theory cannot account for all the alpha-particles. In high energy nucleus-nucleus interactions alpha-particles are produced partly by emission from disintegrating fragments and partly by a knock-on process in which quasi-elastic collisions between nucleons and alpha-clusters take place. This last statement is supported by the fact that alpha-particles are emitted with high momentum components in the forward as well as in the transverse direction.

Abstract. The emission of pions and protons in interactions between heavy nuclei from the cosmic radiation (12 < Z_< 26) and photoemulsion nuclei has been studied. The angular and energy distributions of target protons are similar to corresponding distributions in protonnucleus interactions for emission angles > 30 ~ In heavy ion interactions a forward peak of high energy target protons (E > 200 MeV) is observed. The energy spectrum of target protons for angles < 30 ~ is remarkably fiat for heavy ion interactions. For increasing disintegration of the target nucleus the number of produced pions per emitted recoil target proton is almost constant in heavy ion interactions, while it decreases rapidly in proton-nucleus interactions. The logtgO distributions of pions have small standard deviations even in interactions with a large target disintegration.

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