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Walter Greiner

Publications and source records attributed to Walter Greiner.

97 records · Page 6Linked to original sources
arXiv1996

Microscopic calculation of expanding nuclear matter

Quantum Molecular Dynamics (QMD) calculations are used to study the expansion phase in central collisions between heavy nuclei. The final state of such a reaction can be understood as the result of a entropy conserving expansion starting from a compact source. The properties of this hypothetic source, however, are in conflict with the assumptions used in fireball models. Moreover, this hypothetical source is not formed in the dynamical evolution of the system.

nucl-th↗
arXiv1995

On the impossibility of temperature extraction from heavy ion induced particle spectra

Spectra of various particle species have been calculated with the Quantum Molecular Dynamics (QMD) model for very central collisions of Au+Au. They are compatible with the idea of a fully stopped thermal source which exhibits a transversal expansion besides the thermal distribution of an ideal gas. However, the microscopic analyses of the local flow velocities and temperatures indicate much lower temperatures at densities associated with the freeze-out. The results express the overall impossibility of a model-independent determination of nuclear temperatures from heavy ion spectral data, also at other energies e.g. CERN or for other species (i.e. pions, kaons, hyperons)!

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arXiv1994

A stopped Delta-Matter Source in Heavy Ion Collisions at 10 GeV/n

We predict the formation of highly dense baryon-rich resonance matter in Au+Au collisions at AGS energies. The final pion yields show observable signs for resonance matter. The Delta(1232) resonance is predicted to be the dominant source for pions of small transverse momenta. Rescattering effects -- consecutive excitation and deexcitation of Deltas -- lead to a long apparent lifetime (> 10 fm/c) and rather large volumina (several 100 fm^3) of the Delta-matter state. Heavier baryon resonances prove to be crucial for reaction dynamics and particle production at AGS.

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arXiv1994

Sea-quark Content of Nucleons from Proton-induced Drell-Yan Production

We analyse the proton-induced Drell-Yan production in both the flavor asymmetry and isospin breaking explanations for the violation of the Gottfried sum rule. Consequences from three different forms of corrections to the flavor and isospin symmetric parton distributions are examined. It is found that the calculated results are sensitive to the choices of parameters and parton distributions, and to the ways the corrections are introduced. All three forms of corrections could be consistent with the recent Fermilab Experiment E772 data for the ratio of cross section $R=σ_{W}/σ_{IS}$ and for the shape of the differential cross section $m^{3}d^{2}σ/dx_{F}dm$ for $^{2}$H.

hep-ph↗
arXiv1992

Flavour Distributions in the Nucleons: SU(2) Sea Asymmetry or Isospin Symmetry Breaking?

The Gottfried sum rule violation reported by the New Muon Collaboration(NMC) was interpreted as indication for a flavour asymmetry of the sea quark in the nucleons. We investigate the alternative possibility that isospin symmetry between the proton and the neutron is breaking. We examine systematically the consequences of this possibility for several processes, namely, neutrino deep inelastic scattering, charged pion Drell-Yan process, proton Drell-Yan process, and semi-inclusive deep inelastic scattering, and conclude that a decision between the two alternative explanations is possible.

hep-ph↗
arXiv1992

Finite volume of baryons and the mass limit for neutron stars

We confirmed the following idea by numerical calculation: The extended structure of baryons may make the nuclear equation of state stiffer at higher density while keeping the compression modulus for normal nuclear matter around its empirical value $K=240MeV$.The model built in this wayy fits all empirical data for normal nuclear matter and gives the mass limit of neutron stars compatible with the observation.

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