Study of collective movements: plane flow and azimuthal anisotropy

One of the central problems of the heavy ion physics consists in the characterization of the nucleon-nucleon interaction in the nuclear matter. The study of collective flow appearing during the collisions allows by making use of the dynamical models (BUU, LVUU, QMD, etc.) to access to two basic interaction parameters: the nucleon-nucleon cross section in the nuclear environment, σnn and the nuclear matter incompressibility parameter, K∞. Our study focuses particularly on the matter flow in the reaction plane and on the competition between the emissions in and off the reaction plane for the light particles observed at mid-rapidity. Several experiments were carried out to achieve this aim: 36Ar on 27Al from 55 to 95 MeV/u and 64Zn on 58Ni from 36 to 79 MeV/u with the detector assembly MUR and TONNEAU, 36Ar on 58Ni from 32 to 95 MeV/u and Ni on Ni from 32 to 90 MeV/u with the INDRA multidetector. These detection systems allow obtaining a good classification according to the impact parameter as well as a good reconstitution of the reaction plane. The first results indicate for the the σnn a value of about 80% of the free nucleon -nucleon interaction cross section. Unfortunately, the limited range of the incident energy does not allow extracting so far a value for the K∞. This will be obtained only when the results from the Ni on Ni experiments at GANIL with INDRA and at SIS with FOPI will be combined. The INDRA experiments will provide also the parameter of flow and of anisotropy of H, He and Li