Statistical decay of very hot nuclei-the production of large clusters

TLDR

Heavy ion collisions uniquely reach nuclear matter compressions up to about threefold, yet long‑range Coulomb forces prevent extrapolation to the thermodynamic limit. The review aims to discuss collision‑dynamics theories for extracting the nuclear equation of state, to examine statistical decay of equilibrated hot nuclei, and to introduce a microcanonical Metropolis sampling method. The authors employ a microcanonical Metropolis sampling technique that directly computes microcanonical observables from the partition sum with high statistical precision. From first principles, the study establishes finite‑nucleus thermodynamics, revealing that Coulomb‑induced finite‑size effects produce distinctive phase‑transition signatures and enable nuclei to fragment into large clusters at high excitation.

Abstract

Heavy ion collisions are the only tools that enable us to reach compressions of nuclear matter up to a factor of about three. Theories of the collision dynamics that are necessary in order to extract the equation of state for nuclear matter are discussed. The main part of the review is devoted to the statistical decay of equilibrised very hot nuclei. A new mathematical method, microcanonical Metropolis sampling, which allows the explicit calculation of microcanonical observables directly out of the microcanonical partition sum with high statistics, is presented. Thermodynamics of finite nuclei can thus be established from the first principles. This is important as nuclei subjected to long-range Coulomb forces do not allow extrapolation to the thermodynamic limit. This peculiarity has interesting consequences for the phase transitions and the critical behaviour of nuclei. It is also related to the property of nuclei to break into large clusters at high excitation.