Entropy and light cluster production in heavy-ion collisions at intermediate energies

The entropy production in medium energy heavy-ion collisions is analyzed in terms of ratio of deuteronlike to protonlike clusters ($d_{like}/p_{like}$) using \emph{quantum molecular dynamics} (QMD) model. The yield ratios of deuteronlike-to-protonlike clusters calculated as a function of participant proton multiplicity closely agree with experimental trends. Our model predictions indicate that full thermodynamical equilibrium may not be there even for the central geometry. The apparent entropy extracted from the yield ratios of deuteronlike-to-protonlike clusters, however, reflects the universality characteristics \emph{i.e.} it is governed by the volume of reaction independent of the target-projectile combination. Our calculations for apparent entropy produced in central collisions of Ca+Ca and Nb+Nb at different bombarding energies are in good agreement with $4\pi$ Plastic Ball data.

Yogesh K. Vermani, Rajeev K. Puri · 2010