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HK: Physik der Hadronen und Kerne

HK 8: Elektromagnetische und Hadronische Sonden

HK 8.3: Talk

Monday, March 20, 2006, 17:00–17:15, F

η and π⁰π⁰ photoproduction from complex nuclei — •Thierry Mertens — Basel University, Physic institut, Switzerland

Total photoproduction on the free nucleon shows a bump-like structure around 800 MeV, attributed mainly to the excitation of the D₁₃(1520) and the S₁₁(1535) resonances. Its disappearance for nucleus targets could indicate in-medium modifications of the resonances. Self-consistent calculations of the in-medium spectral functions of mesons and nucleons resonances predict almost no effect on the S₁₁ but a strong broadening of the D₁₃ due to its strong coupling to the ρ. Experimentally those properties can be compared via the study of η (dominated by S₁₁) and double π⁰ (dominated by D₁₃) photoproduction from nuclei. Measurements for carbon, calcium, niobium and lead targets have been done at the ELSA accelerator with the combined Crytall Barrel and Taps detectors. Final results will be discussed in view of the resonance in-medium properties.