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HK: Hadronen und Kerne
HK 48: Electromagnetic Probes VII, Electro-, Photoproduction
HK 48.3: Group Report
Wednesday, March 18, 1998, 15:00–15:30, B
Role of the π N interaction in pion photo–production — •S. Krewald1, O. Krehl1, K. Nakayama2, and J. Speth1 — 1Institut f"ur Kernphysik, Forschungszentrum J"ulich GmbH, 52425 J"ulich — 2Department of Physics and Astronomy, University of Georgia, Athens, GA 30602, USA
It has been shown [1], that the π N final state interaction has large influence on the pion photo–production. We have developed a microscopic model for the π N interaction, which includes the exchange of correlated two pion pairs in the t–channel [2]. This model has been extended recently to include other reaction channels.
We shown that the pion photo–production reaction is extremely sensitive to the off shell behavior of the π N interaction which enters into the final state interaction. The ambiguity in the π N interaction off shell is shown to be introduced, to a large extent, by the hadronic form factors. The pion photo–production reaction therefore probes these hadronic form factors.
The form factor in the γ N → π N potential is found to be rather soft in comparison with the hadronic form factors entering the π N interaction. This finding shows, that a more elaborate theory of the form factors is required. In order to resolve this problem we investigate an improved π N/ρ N coupled channel model for the π N interaction, which takes the hadronic structure of the photon (via vector meson dominance) into account. The influence of the coupling to the ρ N channel for both, hadronic π N interaction and pion photo–production is discussed.
[1] S. Nozawa, T.-S. H. Lee and B. Blankleider, Phys. Rev. C 41 (1990) 213.
[2] C. Schütz, J.W. Durso, K. Holinde and J. Speth, Phys. Rev. C 49 (1994) 2671.