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Accueil du site > Activités scientifiques et techniques > Structure et dynamique > Thèmes de recherche > Multifragmentation

Multifragmentation

Extended studies of the multifragmentation phenomenon on Xe+Sn central and Au+Au mid-peripheral collisions brought new insights on multifragmentation and the related liquid-gas type phase transition of nuclei. The heaviest fragment detected in the decay of quasiprojectiles produced in intermediate energy Au+Au collisions appears as an order parameter of the transition. Its distribution has been observed to be bimodal. This feature is expected as a generic signal of phase transition in nonextensive systems. An estimate of the latent heat of the transition was extracted, 8.1(±0.4)stat(+1.2 -0.9)syst MeV/nucleon (PRL103, 2009, 072701). In addition, from the freeze-out properties of multifragmenting quasi-fused nuclei and using a new quantal method based on proton transverse momentum fluctuations to extract the temperature, constrained caloric curves (relation between the temperature and the internal energy of a system) have been built. At constant average volumes caloric curves exhibit a monotonic behaviour whereas for constrained pressures a backbending is observed. Such results support again the existence of a first order phase transition for hot nuclei (PLB723, 2013, 140).

To initiate studies to be pursued with future exotic beam facilities, isospin effects on multifragmentation properties were investigated thanks to nuclear collisions between different isotopes of xenon beams and tin targets. In central collisions leading to multifragmentation, the mean number of fragments (Z≥5) and their mean kinetic energy increase with the neutron-richness of the total system. Comparisons with a stochastic transport model ruled out secondary decays as the origin of the multiplicity increase and showed that is manifests the effect of the symmetry energy on the multifragmentation process (PRC86, 2012, 044617).


 

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Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
UMR 8608 - CNRS/IN2P3

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