Mesons in Nuclei: η and ω Mesons

摘要

Data on the photoproduction of w mesons on nuclei have been re-analyzed in search for in-medium modifications. The data were taken with the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in Bonn. The extracted w line shape was found to be sensitive to the background subtraction. In experiments at the tagged photon facility of the Mainz MAMI accelerator photopro-duction of mesons from light nuclear targets (deuteron and 3He) has been studied. The experiments used the combined Crystal Ball/TAPS setup in Mainz. Measurements of η- and π~0-photoproduction off a liquid 3He-target have been used for the search for the formation of q-mesic ~3He. The installation of the WASA detector at COSY opened a unique possibility to search for the ~4He-η bound state with high statistics and high acceptance. We are conducting a search via an exclusive measurement of the excitation function for the dd →~3Hepπ~- reaction.