Isoscaling and the symmetry energy in spectator fragmentation

Isoscaling and its relation to the symmetry energy in the fragmentation of excited residues produced at relativistic energies were studied in two experiments conducted at the GSI laboratory. The INDRA multidetector has been used to detect and identify light particles and fragments with Z <= 5 in collisions of 12C on 112,124Sn at incident energies of 300 and 600 MeV per nucleon. Isoscaling is observed, and the deduced parameters decrease with increasing centrality. Symmetry term coefficients, deduced within the statistical description of isotopic scaling, are near gamma = 25 MeV for peripheral and gamma < 15 MeV for central collisions. In a very recent experiment with the ALADIN spectrometer, the possibility of using secondary beams for reaction studies at relativistic energies has been explored. Beams of 107Sn, 124Sn, 124La, and 197Au were used to investigate the mass and isospin dependence of projectile fragmentation at 600 MeV per nucleon. The decrease of the isoscaling parameters is confirmed and extended over the full fragmentation regime covered in these reactions.Comment: Proceedings of the IWM2005, Catania, Italy, Nov 200

Isoscaling in neck fragmentation

Production of intermediate mass fragments (IMF) has been studied in semi-peripheral 124Sn (35AMeV) + 64Ni and 112Sn (35AMeV) + 58Ni reactions. Our recently proposed new method of an analysis of the neck- like fragmentation processes that provides information on the IMFs time equence and time scale is reviewed. Isotopic analysis of so characterized IMFs gives evidence for neutron enrichment of mid-velocity fragments. A clear isoscaling behavior is found despite the short emission time scale. Evolution of the isoscaling parameters from semi-peripheral to central collisions is discussed