Nuclear physics perspectives on high-energy nuclear collisions

Aspects of kinetics in the collision of ultrarelativistic heavy ions with nuclei are considered. First, the prediction of heavy-ion reactions in terms of the reactions induced by a single nucleon are addressed. The deviation of such a prediction from experiment would indicate the presence of new phenomena that are present because of the structure of the incident heavy ion. It would show that it is not possible to regard the latter as a simple collection of nucleons that happen to be traveling together. Experimental results imply that in the collision of an incident proton with a target nucleon energy and momentum are being transferred to the nuclear degrees of freedom in increasingly smaller amounts as the proton energy increases; it seems that the internal degrees of freedom of the nucleon are excited by the collision. The latter half of the paper deals with an analysis of peripheral collisions from the point of view of the Weizsaecker-Williams method. The excitation of collective modes and pion production are among the topics discussed. 4 figures, 1 table