B. M. Waldhauser

Ideal nuclear fluid dynamics at ultra-relativistic energies

We investigate the reaction O+Au at 200 AGeV in an ideal relativistic (3+1)-dimensional one-fluid hydrodynamical model. We correct former calculations which contained acausal matter transport, leading to contradictions with experimental data for the baryonic rapidity distribution. We find that the corrected results are in good agreement with data, casting new light on the question of the applicability of ideal one-fluid hydrodynamics to heavy-ion collisions.

Influence of the nuclear bulk properties and the MIT bag constant on the phase transition to the quark gluon plasma

We consider the influence of the bulk properties of nuclear matter, namely the ground state incompressibility and the effective nucleon mass, and of the MIT bag constant on the phase transition from hadron matter to quark gluon plasma. It is mainly the effective nucleon mass which determines the stiffness of the equation of state and therefore also the behaviour of the phase transition curves. The energy densities in the coexistence region are found to increase for finite chemical potentials and softer equations of state up to 10 GeV/fm3. For small bag constants and for softer nuclear equations of state the phase boundary exhibits unusual deformations, due to the fact that the phase transition sets in already at pressures not too far from the saturation value. Although this would increase the experimental possibility to create the QGP, it is more likely that one must regard bag constants in the range of the original MIT value as not producing a realistic behaviour of the quark-hadron matter phase transition in the context of an MIT bag equation of state for the quark side.

High Energy Nuclear Fluid Dynamics

In the last decade more and more interest has been focussed on the problem of how to deduce the nuclear matter equation of state from experimental data, especially from heavy ion collisions. One has looked not only at densities around saturation to determine the stiffness of the equation of state, but recently also at very high densities (energies) in order to find signals for a phase transition to the quark gluon plasma. One problem is, however, the uncertainty in the bulk properties and the minor significance of the compression constant at ground state on the high density behaviour of the nuclear equation of state. Therefore it is a problem to deduce the equation of state from the ground state properties or vice versa. On the other hand the key mechanism for high compression and heating of nuclear matter in the laboratory was unambiguously established with the discovery of compression shocks in nuclear matter, which had been predicted long ago. Our approach is therefore to study the behaviour of highly excited and more or less compressed nuclear matter by using the successful hydrodynamical model and extend it in order to describe ultrarelativistic heavy ion collisions. Results are presented for collisions of heavy ions at high energies up to 200 GeV in full space and time (3 + 1 dimension) and compared to experimental data.

Sensitivity of pion production to the nuclear EOS and to the delta's coupling constant

A relativistic baryon-meson mean field theory (including delta resonances) is used to study the dependence of pion production in heavy ion collisions on the nuclear equation of state and on the delta-meson coupling constants. For fixed ground state equations of state, the pion yields depend sensitively on the value of the delta-meson coupling constants.

Constraints on the equation of state for neutron stars from fast rotating pulsars

We analyze the restriction on the equation of state for neutron stars given by the more or less known masses (1.445 ± 0.007M ⊙ and 1.85 ± 0.30M ⊙) of neutron stars and the also more or less known frequencies of fast rotating pulsars like PSR1957+20 (Ω = 4033 Hz) and perhaps by a newborne pulsar in the supernova SN1987A (Ω = 12369 Hz), where the latter one is seen only by one group for 8 hours and then never again. Softer equations of state generally yield stable rotating pulsars of lower mass, while stiffer ones are leading to heavier neutron stars.