Constrained caloric curves and phase transition for hot nuclei

TL;DR

This paper uses experimental data and simulations to construct caloric curves of hot nuclei, providing evidence for a first order phase transition in nuclear matter.

Contribution

It introduces a method to analyze event-by-event freeze-out properties and constructs constrained caloric curves revealing phase transition signatures.

Findings

Caloric curves show monotonic behavior at constant volume.

Backbending observed in caloric curves under constrained pressure.

Results support the existence of a first order phase transition in hot nuclei.

Abstract

Simulations based on experimental data obtained from multifragmenting quasi-fused nuclei produced in central $^{129}$Xe + $^{nat}$Sn collisions have been used to deduce event by event freeze-out properties in the thermal excitation energy range 4-12 AMeV [Nucl. Phys. A809 (2008) 111]. From these properties and the temperatures deduced from proton transverse momentum fluctuations, constrained caloric curves have been built. At constant average volumes caloric curves exhibit a monotonic behaviour whereas for constrained pressures a backbending is observed. Such results support the existence of a first order phase transition for hot nuclei.