Simulations of the zero degree detector response (part of the 4Π detector implanted at GSI-Darmstadt); study of Fai and Randrup model and contribution at the detector resolution

The study developed in this thesis concerns simulations of the zero degree detector or inner wall which is a part of the 4Π detector implanted at G.S.I.-Darmstadt; On the other hand, we study the collective flow of nuclear matter in the reaction plane. These simulations are based on the statistical model of G. FAI and J. RANDRUP which is performed by the computer code FREESCO which generates the particles emitted from the collision. Some results extracted from this code show that the multiplicity of particles and fragments emitted from the Au + Au collision at 1 GeV/u is very high and that half of these particles and fragments are neutral ones. The simulation of the inner wall takes into account, for the particles and fragments emitted between 0 and 7.5 degrees, the calculation of the energy loss, the fluctuations of that energy loss and the Coulomb multiple scattering in the different materials between the target and the inner wall. The results of these simulations show the good identification of the different charges detected on the inner wall and exhibit the good efficiency of this detector. The resolution of the reaction plane reconstruction is in qualitative agreement with the experimental results of the plastic Ball but the calculations do not allow extracting a nuclear matter flow value from the only inner wall data. Nevertheless a value of this observable can be extracted quite well from the data of the 00-300 range, corresponding to the whole plastic wall of the 4Π detector at G.S.I.-Darmstadt