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

What can be learned from heavy-ion central collisions around the Fermi energy

XL Bormi

The Fazia initiative: more powerful detectors for a more detailed investigation on the origin and the decay of charged fragments

International audienceThe main results of the R&D program of the FAZIA collaboration are described. The objective was to improve particle identication capabilities from solid-state telescopes made of Silicon detectors and CsI(Tl) scintillators in view of a new large acceptance apparatus to be used for heavy-ion physics. Important progresses have been made on silicon detectors thanks to a careful control of the material, of its doping uniformity and of the crystal orientation. Moreover, the use of appropriate fast digital electronics allowed to extract maximum information via Pulse Shape Analysis and to propose new configurations of CsI(Tl) readout. Some of the recent results of the telescopes are discussed here, together with some perspective and preliminary data on the physics program at intermediate bombarding energie

Isospin transport in 84Kr+112-124Sn collisions at Fermi energies with the FAZIA detector

Isotopically resolved fragments up to Z 20 have been studied in a test experiment by the FAZIA Collaboration with a three-stage telescope. The reactions 84Kr+112Sn (n-poor) and 84Kr+124Sn (n-rich) at 35 MeV/nucleon were measured. The telescope was located near the grazing angle, so the detected fragments are mainly emitted from the phase-space region of the projectile. In the following, evidences for isospin diffusion and drift will be discussed

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