Thermodynamic Variables from Spectator Decay

New results for the masses, excitation energies, temperatures, and densities of excited spectator systems at breakup are presented. They were obtained in two recent experiments with the ALADIN spectrometer at SIS in which reactions of Au-197 on Au-197 in the regime of relativistic energies up to 1 GeV per nucleon were studied. The methods used to extract these thermodynamic variables are discussed.Comment: 17 pages, TeX with 10 included figures; To appear in the proceedings of the 14th Winter Workshop on Nuclear Dynamics, Snowbird, Utah, January 31 - February 7, 1998; also available from http://www-kp3.gsi.de/www/kp3/aladin_publications.htm

Hot fragmentation of nuclei

Today, we have a variety of reactions at hand that can be used to multi-fragment nuclei. In many of these reactions even several sources of fragments can be discerned and characterized. There is overwhelming evidence that these sources of fragments are hot. It is already less clear whether heat by itself is sufficient to initiate the fragment decay. What causes fragmentation, and when and how are the fragments (pre)formed? These questions have remained as much a challenge as the complementary class of questions to which they are related: What observations derive their significance from the liquid-gas phase behavior of extended nuclear matter? And, can we observe a phase transition in finite nuclei? Recent developments, largely coming from complex analyses of data sets measured in 4-pi-type experiments as well as from calculations based on advanced theoretical concepts, will be discussed.Comment: 13 pages, with 8 included figures; To appear in the proceedings of the NN 2000 conference; Also available from http://www-kp3.gsi.de/www/kp3/aladin_publications.htm

Probing the quantum-mechanical equivalent-photon spectrum for electromagnetic dissociation of relativistic uranium projectiles

Electromagnetic fission cross sections for the reactions U + (Be, C, Al, Cu, In, Au, U) at E/A = 0.6 and 1.0 GeV are compared to theoretical calculations using recently proposed quantum-mechanical equivalent-photon spectra. In contrast to semi-classical calculations, systematically lower cross sections are obtained that cannot reproduce the experimental results. Furthermore, we point out that the study of electromagnetic fission cross sections or electromagnetic 1-neutron removal cross sections alone cannot provide unambiguous information on the excitation of the double giant dipole resonance.Comment: 4 pages, TeX, psfig, also available at http://csa5.lbl.gov/moretto/ps/emd_qm.ps, submitted to Phys. Rev.

Modification of surface energy in nuclear multifragmentation

Within the statistical multifragmentation model we study modifications of the surface and symmetry energy of primary fragments in the freeze-out volume. The ALADIN experimental data on multifragmentation obtained in reactions induced by high-energy projectiles with different neutron richness are analyzed. We have extracted the isospin dependence of the surface energy coefficient at different degrees of fragmentation. We conclude that the surface energy of hot fragments produced in multifragmentation reactions differs from the values extracted for isolated nuclei at low excitation. At high fragment multiplicity, it becomes nearly independent of the neutron content of the fragments.Comment: 11 pages with 13 figure

Collective flow in heavy ion collisions at intermediate energies

We present results of a flow analysis for the set of reactions of 124,129Xe projectiles and 112,124Sn targets at incident energies 100 and 150 A MeV studied with the INDRA detector at GSI. The dependence on centrality and on p_t of the directed and elliptic flow are determined for isotopically selected reaction products with Z \le 3. The flow parameters v_1 and v_2, in general, follow expected trends but isotopic effects are small.Comment: 3 pages, 2 figures, contributed talk at INPC, Tokyo, June 3-8, 2007, to appear in the proceeding