Frammentazione di ioni pesanti relativistici alle energie del Bevalac

Two experiments bave been, recently, carried out at the Lawrence Berkeley Laboratory Bevalac Hiss facility: the EOS and the TRANSPORT experiments. $EOS experiment.$ The EOS collaboration has completed an exclusive study of relativistic heavy ion collisions at the Bevalac using a variety of projectile, target and beam energy combinations. Energy spectra of hydrogen and helium isotopes emitted in Au+Au collisions at energies ranging from 0.25 to 1.15 GeV/A have been measured. A systematic study of the shapes of the spectra reveals a significant non-thermal component consistent with collective radial flow. Comparison of the flow signai to predictions of QMD and BUU models are made. The moments of the resulting charged fragment distribution provide evidence that nuclear matter possesses a critical point observable in finite nuclei. Values for critical exponents gamma, beta and tau bave been determined these values are close to those for liquid-gas systems and different from those for 3D percolation. $Transport experiment.$ A liquid hydrogen target was used to study nuclear fragmentation of beams of relativistic heavy ions, over an energy range 400 to 900 MeV/A. The experiment was carried out at the Lawrence Berkeley Laboratory Bevalac Hiss facility, using the charge-velocity-rigidity method to identify the charged fragments. Here we present total charge-changing cross sections obtained from 17 separate runs. These new measured cross sections display an energy dependence which follows semiempirical model predictions. The isospin of the projectiie nuclei also appears to be an important factor in the interaction process.