[en] Incomplete fusion or massive transfer mechanisms were invoked to explain the observed distributions of products, especially for heavy residues, for the nearly symmetric systems, ³⁶Ar on ²⁷Al from 55 to 95 MeV/u, and ⁶⁴Zn on ^natTi, from 35 to 79 MeV/u. Charged products were detected in a nearly 4π geometry using two complementary multidetector systems. Lorentz invariant cross section maps plotted for different products show three sources for Z=1 and 2 particles: quasi-projectile, quasi-target and a third source, located at mid-rapidity. For heavier fragments, the mid-rapidity contribution vanishes. (K.A.)

[en] Charmonium state production in pA and S-U collisions is reported on. Experimental data are reviewed. The present status of the interpretation of charmonium suppression is discussed. Finally new preliminary results about Pb-Pb collisions are presented. (author)

[en] Properties of nearly all final products observed in particular heavy ion collisions are presented. They concern the vaporization events detected with the 4π array INDRA, where all detected species have atomic numbers lower than 3. Data were obtained over a broad excitation energy range (8-28 AMeV). The occurrence of thermodynamical equilibrium is discussed by comparing the data with the results of two statistical models. Finally, a comment is made on the temperature extracted from the Z=1 and Z=2 isotopic ratios in relation to findings obtained with heavier isotopes in another experiment. (author)

[en] For the first time, INDRA has been used to analyse resonances observed in correlation functions, giving thus the possibility to probe the caloric curve (correlation between the excitation energy and the temperature). First results obtained for the reaction ₁₈³⁶Ar+₂₈⁵⁸Ni at 95 MeV/nucleon are presented where the projectile-like apparent temperature has been evaluated. Moreover, the measured populations of excited states are compared with the predictions of a statistical model which includes an original hypothesis of excluded volume for species at the freeze-out. (author)

[en] A search for the reaction of coherent dissociation ¹²C → 3α on carbon nuclei at 4,2 GeV/c per nucleon has been made. The cross section of this reaction and its dependence on mass number of nucleus were evaluated. The competitive analysis of the momentum and correlation characteristics of secondary alpha particles in the laboratory and center-of-mass frames of fragmenting nucleus with the incoherent events and with the same data for heavy targets was carried out. It was shown that the mechanism of ¹²C → 3 α decay is essentially changing with target nucleus and depends on the type of nucleus-nucleus interaction. We have also measured the yield of protons, deuterons, tritons and fragments with z ≥ 2 and investigated their transverse momenta distributions in the laboratory frame and in the frame with Σ_ip_Ti = ) for all charged fragments. The nonmonotonic dependence of the degree of colinearity of the transverse momenta of alpha particles in the azimuthal plane of the reaction ¹²C → 3α at 4,2 GeV/c per nucleon on the excitation energy of the carbon nucleus has been observed. (author)

[en] This thesis is composed of four chapter. The first one presents a quantum mechanical model able to describe the light particle correlations by taking into account the nuclear and Coulomb final state particle interactions as well as the influence of the Coulomb field of the emitting nucleus. This model was applied to the analysis of the experimental data obtained from the sequential di-excitation of a quasi-projectile formed in the ¹²⁹ Xe + ⁴⁸ Ti at 45 MeV/nucleon. An adaptation of the SPEG spectrometer allowed the measurements of the proton-proton coincidence studies in the range of very low relative momenta (1-10 MeV/c). For such values the proton-proton correlation function is sensible indeed to the proton emission time separation. In case of the protons, the analysis allowed to deduce a lifetime value exceeding 1500 fm/c while for the p-d, d-d and t-t particle couples, the lifetime values were much shorter. This study showed that the deuterons as well as the tritons and alpha particles are emitted prior to the proton emission. The limits of the description of particle emission from a static source have led to consider the influence of dynamical phenomena on the correlation function. This approach made use of a QMD transport model.. The important influence on the correlation function of the dynamic correlations between the momenta and space-time coordinates of the emitting particles was made evident. It is pointed out that the experimental proton-proton correlation function was not possible to be reproduced through QMD theoretical predictions. The momentum variations observed between the particle emission moment in a mean field and its asymptotical value, points to the necessity of a fine description of the interactions

[en] Time-Dependent Hartree-Fock simulations of the evolution of excited gold fragments have been performed. The observed dynamics appears more complex than the collective expansion picture. The minimum density is often not reached during the first density oscillation because of the beating of several collective compression modes. (author)

[en] Nucleus-nucleus collisions at low incident energy are mainly governed by statistical dissipative processes, fusion and deep inelastic reactions being the most important ones. Conversely, in the relativistic energy regime, dynamical effects play a dominant role and one should apply a participant-spectator picture in order to understand the data. In between, the intermediate energy region is a transition one in which it is necessary to disentangle dynamics from statistical effects. Moreover, the Fermi energy region corresponds to available energies comparable with nuclear binding energies and one may except to observe phase transition effects. Experiments performed recently with 4π devices have given quite new data and a much better insight into involved mechanisms and hot nuclear matter properties. INDRA data related to reaction mechanisms and multifragmentation are presented. (author)

[en] The geometry of the critical fluctuations for a general system undergoing a thermal second-order phase transition is investigated. Adopting a generalized free-energy for the local description of the fluctuations of the order parameter at the critical temperature it is shown that instanton-like configurations corresponding to the minima of the free-energy functional, build up clusters with fractal geometry characterizing locally the critical fluctuations. For sufficiently small coarse-graining scales these configurations dominate the partition function and provide an exact description of the critical system. The connection between the corresponding (local) fractal dimension and the critical exponents is derived. Implications of these ideas to chiral QCD phase transition in relativistic heavy ion collisions are also discussed. (author)

[en] Experiments described in this paper are inverse kinematics studies of fission and nuclear fragmentation reactions of a ²³⁸U primary beam at relativistic energies on Pb and Be targets performed at the GSI Fragment Separator. The fragment isotopic distributions have been measured. The projectile fragmentations has been also studied. The isotopes transmitted by the FRS having a magnetic rigidity (B ρ) lower then 10 % of that of projectile are shown. One finds the back-going fission fragments in the projectile framework (more rich in neutrons) and products of the nuclear collisions having an important dissipation in energy, leading to deficient neutron fragments. The isotopic production cross sections of fragmentation process are compared with results of a simulation with the EPAX code. Results for uranium fragments close in charge and mass of ²³⁸U projectile ware obtained. Particularly, the influence of fission in the decay of primary fragments was studied and fission cross section measurements for secondary targets of several actinides revealing the transition of the fission asymmetric mode to the symmetric fission for N = 138, were measured. These two experiments have led to a new collaboration aiming to apply this cross sections measurement method to the study of inverse kinematics induced reactions in heavy targets by high energy protons. These measurements are of great interest for the current developments of the hybrid system concept of coupling an accelerator to a reactor for waste transmutation or electricity productions