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In a search for ω mesic states, the production of ω-mesons in coincidence with forward going protons has been studied in photon induced reactions on 12 C for incident photon energies of 1250 -3100 MeV. The π 0 γ pairs from decays of bound or quasi-free ω-mesons have been measured with the CBELSA/TAPS detector system in coincidence with protons registered in the MiniTAPS forward array. Structures in the total energy distribution of the π 0 γ pairs, which would indicate the population and decay of bound ω 11 B states, are not observed. The π 0 γ cross section of 0.3 nb/MeV/sr observed in the bound state energy regime between -100 and 0 MeV may be accounted for by yield leaking into the bound state regime because of the large in-medium width of the ωmeson. A comparison of the measured total energy distribution with calculations suggests the real part V 0 of the ω 11 B potential to be small and only weakly attractive with V 0 (ρ = ρ 0 ) = −15± 35(stat) ±20(syst) MeV in contrast to some theoretical predictions of attractive potentials with a depth of 100 -150 MeV.

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The first measurements of the beam-target-helicity-asymmetries E and G in the photoproduction of ω-mesons off protons at the CBELSA/TAPS experiment are reported. E (G) was measured using circularly (linearly) polarised photons and a longitudinally polarised target. E was measured over the photon energy range from close to threshold (E γ = 1108 MeV) to E γ = 2300 MeV and G at a single energy interval of 1108 < E γ < 1300 MeV. Both measurements cover the full solid angle. The observables E and G are highly sensitive to the contribution of baryon resonances, with E acting as a helicity filter in the s-channel. The new results indicate significant s-channel resonance contributions together with contributions from t-channel exchange processes. A partial wave analysis reveals strong contributions from the partial waves with spin-parity J P = 3/2 + , 5/2 + , and 3/2 − .