Parts | Days | Selection | Search | Downloads | Help
HK: Hadronen und Kerne
HK 34: Heavy Ion Reactions IV, Relativistic Energies
HK 34.1: Group Report
Tuesday, March 17, 1998, 17:00–17:30, P
Thermodynamic evolution in heavy ion reactions∗ — •T. Gaitanos, M. Rempter, and H. H. Wolter — Sektion Physik, Univ. München, 85748 Garching
The determination of temperatures in heavy ion reactions is of
particular interest with respect to the investigation of the
caloric equation of state and of liquid-gas phase transitions.
In this work we attempt to determine the thermodynamical evolution
of the nuclear medium in a heavy ion collision directly from the phase
space distribution of a transport theoretical calculation. We
use a relativistic treatment with gaussian test particles which
yields smooth phase space distributions and allows to determine
locally density, pressure, collective velocity and temperature.
For the latter we describe the local momentum
distributions in terms of an antisymmetrized superposition of two
finite temperature Fermi distributions [1]. Thus non-equilibrium
effects are taken into account and are not interpreted as temperature.
In this way the thermodynamical state of nuclear matter is
characterized locally and temporally.
We applied this approach to central and peripheral Au+Au
reactions which were also extensively investigated by the FOPI
collaboration [2]. We discuss the evolution in the spectator and in
the participant region. By discussing the effective incompressibility
from the pressure-density relation we determine regions of
thermodynamical instability. The temperature and density conditions
found in the spectator matter are consistent with experimental
indications for the occurence of phase transitions. We also
determine radial flow for non-central points and compare with
blast szenarios. In our approach fragments are described
in an qualitative fashion in a coalescence model. We investigate the
temperature at which fragments are formed, which is of relevance to
the question of comparing different isotope thermometers.
[1] C. Fuchs, P. Essler, T. Gaitanos, H. H. Wolter,
Nucl. Phys. A in press.
[2] W. Reisdorf (FOPI Collaboration), Nucl. Phys. A 612 (1997) 493 ∗ supported by aggrant of BMBW, 06LM363.