Tübingen 2003 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 6: Physik mit schweren Ionen I

HK 6.10: Talk

Monday, March 17, 2003, 18:30–18:45, E

Fragmentation in Peripheral Heavy-Ion Collisions: From Neck Emission to Spectator Decays — •Jerzy Łukasik — GSI, Darmstadt, Planckstr. 1, D-64291 Darmstadt

Invariant cross sections of intermediate-mass fragments in peripheral collisions of ¹⁹⁷Au on ¹⁹⁷Au at incident energies between 40 and 150 AMeV have been measured using the 4π multi-detector INDRA and the beams from the SIS synchrotron at the GSI Darmstadt.

The observed shapes and trends of the invariant cross section distributions are difficult to be explained satisfactorily by either the available statistical or dynamical models.

An extended Goldhaber model, introduced in order to identify the basic ingredients that govern the evolution of the fragment production mechanisms in the transition region between the Fermi energy and relativistic energies, demonstrates that the observed cross-section distributions and their evolution result predominantly from the coalescence requirement for the emerging fragments and from the Coulomb repulsion between the fragment and the heavy residues. The quantitative comparison with transverse energy spectra and fragment charge distributions emphasizes also the role of hard scattered nucleons, Pauli blocking, Fermi motion and nucleon mixing in the fragmentation process.

As an important result, it was found that the same criteria are at work throughout the covered energy range.