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HK: Hadronen und Kerne

HK 55: Structure of Baryons, Mesons VIII, Theory

HK 55.2: Gruppenbericht

Mittwoch, 18. März 1998, 14:30–15:00, J

Thermodynamics with resonant states — •Wolfgang Weinhold, Bengt Friman, and Wolfgang Nörenberg —
Gesellschaft für Schwerionenforschung (GSI),
Planckstr. 1, D-64291 Darmstadt, Germany
and
Institut für Kernphysik, Technische Universität Darmstadt,
Schloßgartenstr. 9, D-64289 Darmstadt, Germany
We present an approach to the thermodynamics of strongly interacting hadronic matter including resonant states, based on the Green-function technique of Baym and Kadanoff. In the low density limit we reproduce the results of the virial expansion for the thermodynamic potential and the S-matrix formulation of statistical mechanics.

As an example we consider an interacting system of pions and nucleons including the resonant πN P₃₃ channel. We present an instructive diagrammatic interpretation of the different contributions to the total baryon number. A generalization to resonances with several decay channels – such as the πN S₁₁(1535) resonance which couples strongly to πN and ηN – is given.

Finally, we examine within a simple fireball model – including collective expansion as well as Coulomb final-state interaction – the consequences for particle ratios and particle spectra observed in heavy-ion collisions at intermediate energies.

[1] W. Weinhold, B. Friman, W. Nörenberg, GSI-preprint 97-59,
nucl-th/9710014