Isospin effects in central heavy-ion collisions at Fermi energy

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.