Entropy production in high energy collisions

Abstract

The entropy production in high-energy collisions is computed in a Monte Carlo cascade model. For collisions of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ on ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 800 MeV/nucleon beam energy, the computed entropy is 4.4 per particle, about a unit higher than estimated from bulk dynamics. The particle correlation function of the final state is also computed, and is found to be in reasonable accord with a thermal distribution of the same entropy. With such low entropy values, most of the particles emerge in clusters, contrary to experiment. Thus the cascade calculation supports the conclusion of Siemens and Kapusta, that additional degrees of freedom become accessible in heavy ion collisions, beyond those in a conventional nuclear description.