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HK: Fachverband Physik der Hadronen und Kerne
HK 20: Physik mit schweren Ionen
HK 20.2: Vortrag
Dienstag, 11. März 2008, 09:00–09:15, 2E
Low-density nuclear symmetry energy in heavy ion collisions — •Hermann Wolter1, Maria Colonna2, Massimo Di Toro2, and Joseph Rizzo3 — 1Universität München, Garching, Germany — 2LNS-INFN, Catania, Italy — 3Univ. di Firenze, Florence, Italy
The density dependence of the nuclear symmetry energy has received great interest recently, because of its role in the structure of exotic nuclei and in astrophysical processes. Heavy ion collisions provide an important way to obtain information about this in the laboratory, via interpretation of experimental data with stochastic transport simulations. In this report we investigate the symmetry energy below normal density, which is probed in collisions around the Fermi energy regime. We review our work on several nucleon and fragment observables with respect to their sensitivity to the symmetry energy. In central collisions ratios of emitted nucleon and light fragment yields are investigated, where we increase the sensitivity by using shifted double ratios. In peripheral collisions we study isospin transport between collision partners of different asymmetry in terms of the total kinetic energy loss to isolate symmetry energy effects. We also identify the ratio of the asymmetry of a neck fragment relative to that of the residues as a very sensitive observable. However, comparison with existing experimental data still does not yield a coherent picture of the isovector equation-of-state. Experiments with radioactive beams of greater asymmetry should increase the sensitivity.
Work supported by BMBF, grant 06LM189 and DFG Cluster Origin and Structure of the Universe.