Isospin effects in central heavy-ion collisions at Fermi energy

E Galichet,M.-F Rivet,B Borderie,F Gagnon-Moisan,R Roy,M Colonna

doi:10.1051/epjconf/20123100017

Abstract

N/Z effects were observed on variables measured in central Xe on Sn collisions around the Fermi energy. Comparisons were made with dynamical simulations of collisions in which the symmetry term of the EOS was varied. In this framework it appeared that the observed effects were due to the dynamics of the reaction and not to the deexcitation of the hot primary fragments. The elaboration of the Equation of State (EOS) for nuclear matter requires more experimental constraints, particularly for the formulation of an adequate symmetry term whose density dependence at sub- and supranormal density is still debated. Isospin dependent observables measured in reactions induced by judiciously chosen projectile-target couples already provide some hints on the symmetry term; the derived form is however highly model-dependent. Thus cross-checks making use of a large body of variables and models are necessary to obtain reliable information.

Highlights

Beams of 32 and 45 A MeV 124,136Xe accelerated by the GANIL facility impinged on 112,124Sn targets
Head-on collisions (b=0) were simulated with the stochastic mean field (SMF) calculation described in ref [4, 5]; the same code was used in ref [6] to extract information on the symmetry energy from isospin diffusion
The isoscalar Equation of State (EOS) is soft (K∞=200 MeV), and two parameterisations of the potential part of the symmetry energy are used, an asystiff one linearly increasing with density while the asysoft term (SKM*) has a maximum at normal density

Summary

Introduction

Beams of 32 and 45 A MeV 124,136Xe accelerated by the GANIL facility impinged on 112,124Sn targets. It was observed that the average charged product and lcp multiplicities decrease when the system becomes more neutron-rich whereas the fragment multiplicity increases. The isoscalar EOS is soft (K∞=200 MeV), and two parameterisations of the potential part of the symmetry energy are used, an asystiff one linearly increasing with density while the asysoft term (SKM*) has a maximum at normal density.

Results

Conclusion