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Abstract The present thesis is concerned with the study of two mechanisms of heavy ion nuclear collisions at high energies. The first one is the ”direct stripping reaction” while the second one is the ”fire-ball model” . The thesis consists of two parts. In the first part the angular distribution of the following nuclear reactions; 6Li + Emulsion ~ d + X~ 6Li + Emulsion ~ 4He +X·, 12C+ (A& BT) 12C+H 12C+CNO ~ (Z=2) + X~ ~ (Z=2) + X~ ~ (Z=2) + X and 12C + Emulsion ~ (Z=3 or Z=4 or Z=5) + X. are studied in the framework of direct stripping mechanism at incident momentum (4.5 A GeV/c) where ”X” is the residual nucleus. [In this model one considers the projectile consisting of two clusters, one of them is absorped by the target and the other continuous its flight without any change]. In the second part the angular distribution of the following nuclear reactions ~ -1- 56Fe + Emulsion -4 4He + X~at = 1.7 GeV/A ~ 40Ar + Emulsion ~ 4He + X~at = 2.0 GeV/A ~ 160 + Emulsion ~ 4He + X~ at = 2.1 GeV/A ~ 20Ne + Emulsion ~ 4He + X~ at = 3.6 GeV/A ~ 20Ne + Emulsion ~ P + X~at = 3.6 GeV/A ~ 28Si+ Emulsion ~ 4He + X~ at = 3.6 GeV/A and 28Si+ Emulsion -4P + X; at = 3.6 GeV/A. are calculated in the framework of the ”fire-ball model”. [In this model, the fire-ball is formed in the overlapping region between relativistic heavy ion projectile and target nucleus]. from the obtained results we may conclude that :- (1) The loosely bound projectile nuclei are well explained by the direct stripping mechanism at high energy. this mechanism shows an agreement with experimental data for outgoing fragments with Z<3. For outgoing fragments which have Z> 3, the agreement between theoretical calculations and experimental data is not quite complete. The fragments with Z > 3 seem to be emerging from a formed fire-ball region in a non-equilibriwn stage. (II) The kinetic temperature T (Me V) of the fire ball depends on the incident energy per nucleon. (III) The kinetic temperature T (Me V) of the fire-ball does not depend on the projectile nuclear masses at the same incident energy. -n- -- ------------- ----------- (IV) The kinetic temperature T (Me V) of the fire-ball does not depend on the multiplicity of the outgoing particles at the same incident energy. |