The behavior of constrained caloric curves as ultimate signature of a phase transition for hot nuclei, B. Borderie, CNRS-IN2P3/Institut de Physique Nucléaire/Université Paris-Sud 11, France − Experimental data obtained from multifragmenting quasi-fused nuclei produced in central 129Xe+natSn collisions and related simulations [1] have been used to deduce event by event freeze-out properties on the thermal excitation energy range 4-12 AMeV.  From such properties and by using, on protons emitted at freeze-out, a new thermometer based on quantum momentum fluctuations [2], constrained caloric curves have been derived.  At constant average volumes caloric curves exhibit a monotonous behavior whereas for constrained pressures backbending are observed.  Those results definitively sign the existence of a first order phase transition for hot nuclei.

 

[1] S. Piantelli et al., Nucl. Phys. A809 (2008) 111.

[2] H. Zheng and A. Bonasera, Phys. Lett. B696 (2011) 178.