Research on critical behaviour during fragmentation of the projectile in the Xe+Sn (at 50 MeV/A) reaction

The study of moments of fragments charge distributions produced in heavy ions collisions can give us evidence of a critical behavior of nuclear matter which could explain the multifragmentation pattern. From an experimental point of view, in order to perform this capabilities of the INDRA detector has made it possible to identify all these particles and to reconstruct the initial projectile-like fragment coming from binary collisions in the reaction Xe+Sn at 50 MeV/A. We have selected events where the initial projectile-like fragments keep their entire charge in a large range of excitation energy. The study of these fragment's characteristics show clearly a change in the deexcitation pattern. The evolution of moments of the fragment charge distributions has been reproduced within a percolation model, in this sense we can interpreter this change in the deexcitation pattern as a function of the initial projectile-like fragment's size shows the existence of finite-size effects. However, the signature of a phase transition remains independent on the projectile-like fragment's size. (author). 74 refs., 58 figs., 9 tabs