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HK: Hadronen und Kerne

HK 20: Structure of Baryons, Mesons III, Theory

HK 20.5: Talk

Monday, March 16, 1998, 18:30–18:45, H

Quantum Field Theoretic model for the π-ρ-system — •H. van Hees and J. Knoll — Gesellschaft für Schwerionenforschung mbH, Planckstr. 1, 64291 Darmstadt

The properties of ρ-mesons interaction with pions are investigated within a renormalizable non abelian vector meson dominance model of hidden gauge type. The model is gauge invariant and besides the coupling of rho-meson to the pions contains three and four rho-meson vertices and corresponding ghost contributions. The ρ-meson mass is generated by spontanous symmetry breaking. The self-energies of both mesons are calculated in a selfconsistent approximation at the 1-loop-level using the Schwinger-Keldysh real time formalism. The parameters and the renormalization scheme are fixed at the vacuum level to the masses and the electromagnetic form factor of the pion. Given this self consistent scheme the in medium effects for the mass and width of the ρ- and π-meson as a function of temperature and chemical potential are discussed.

The self consistent approximation is derived from a variational principle using the functional of Luttinger and Ward, which due to Baym leads to a conserving and thermodynamically consistent approximation at any loop level of the functional.