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HK: Hadronen und Kerne
HK 55: Structure of Baryons, Mesons VIII, Theory
HK 55.2: Group Report
Wednesday, March 18, 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