Isospin dynamics and the isospin dependent EOS

Isotopic yields for light particles and intermediate mass fragments have been measured for 112Sn+112Sn, 112Sn+ 124Sn, 124Sn+112Sn and 124Sn+ 124Sn with the Large Area Silicon Strip Array (LASSA). LASSA consists of nine individual telescopes with each telescope comprised of two Si strip silicon detector layers backed by four CsI(Tl) crystals. LASSA provides high angular, energy and isotopic resolution over a large detection area and energy range. The total solid angle covered by LASSA is about 540msr with polar angle 7°--58° and an angular resolution of +/-0.43°. The energy range covered is E/A = 2.4--140 MeV for protons and E/A = 4.8--335 MeV for 16O.;Isotopic yields from central collisions were compared with predictions of stochastic mean field calculations. These calculations predict a sensitivity of the isotopic distributions to the density dependence of the asymmetry term of the nuclear equation of state. However, the secondary decay of the excited fragments modifies significantly the isotopic distributions produced by the stochastic mean field model. The predicted final isotope distributions after decay are narrower and more neutron-rich than the experimental data and the sensitivity of the predicted yields to the density dependence of the asymmetry term is reduced. The distributions calculated using the stiff asymmetry term are more neutron-rich and are closer to the measured values. However the less than satisfactory level of agreement between theory and experiment precludes definitive statements about the density dependence of the asymmetry term of the EOS.;Energy spectra and average energy of light particles and fragments from central collisions were obtained and compared with statistic models calculations. We found that neutron deficient isotopes are significantly more energetic than those of neutron rich isotopes of the same element. This trend is well beyond what can be expected for the bulk multi-fragmentation of an equilibrated system. It can be explained, however, if many of these fragments are evaporated from the surface of the system while it is expanding and cooling.;Measurements of particles and fragments from peripheral collisions were used to study the dynamics in nuclear reactions. Isoscaling analyses imply that the quasi-projectile and quasi-target in these collisions do not achieve isospin equilibrium, permitting an assessment of the isospin transport rates. We find that comparisons between isospin sensitive experimental and theoretical observables, using suitably chosen scaled ratios, permit investigation of the density dependence of the asymmetry term of the nuclear equation of state. This observable appears to be one of those promising ones for providing much needed constraints on the asymmetry at sub-saturation density.