Experimental constraints on the ω –nucleus real potential

Abstract 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 −1  sr −1 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 ω -meson. 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.