Isospin effects and symmetry energy studies with INDRA

The equation of state of asymmetric nuclear matter is still controversial, as predictions at subsaturation as well as above normal density widely diverge. We discuss several experimental results measured in heavy-ion collisions with the INDRA array in the incident energy range 5-80 MeV/nucleon. In particular an estimate of the density dependence of the symmetry energy is derived from isospin diffusion results compared with a transport code: the potential part of the symmetry energy linearly increases with the density. We demonstrate that isospin equilibrium is reached in mid-central collisions for the two reactions Ni+Au at 52 MeV/nucleon and Xe+Sn at 32 MeV/nucleon. New possible variables and an improved modelization to investigate symmetry energy are discussed.Comment: Review for the special issue of EPJA on symmetry energy. 20 pages, 16 figure

Isotopic effects in multifragmentation and the nuclear equation of state

Isotopic effects in spectator fragmentations following heavy-ion collisions at relativistic energies are investigated using data from recent exclusive experiments with SIS beams at GSI. Reactions of 12C on 112,124Sn at incident energies 300 and 600 MeV per nucleon were studied with the INDRA multidetector while the fragmentation of stable 124Sn and radioactive 107Sn and 124La projectiles was studied with the ALADIN spectrometer. The global characteristics of the reactions are very similar. This includes the rise and fall of fragment production and deduced observables as, e.g., the breakup temperature obtained from double ratios of isotope yields. The mass distributions depend strongly on the neutron-to-proton ratio of the decaying system, as expected for a simultaneous statistical breakup. The ratios of light-isotope yields from neutron-rich and neutron-poor systems follow the law of isoscaling. The deduced scaling parameters decrease strongly with increasing centrality to values smaller than 50% of those obtained for the peripheral event groups. This is not compensated by an equivalent rise of the breakup temperatures which suggests a reduction of the symmetry term required in a liquid-drop description of the fragments at freeze-out

Collective motion and kinetic energy fluctuations in central nuclear collisions studied with IN-DRA

ibide

Multifragmentation in central collisions at intermediate energies: a fast process?

XL Bormi

Spectator fragmentation induced by relativistic 12^{12}C projectiles

Matière NucléaireInternational audienc