Mesons in Nuclei: eta and omega mesons

Abstract

Data on the photoproduction of omega 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 omega line shape was found to be sensitive to the background subtraction. In experiments at the tagged photon facility of the Mainz MAMI accelerator photoproduction 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 eta- and pi0-photoproduction off a liquid 3He-target have been used for the search for the formation of eta-mesic 3He. The installation of the WASA detector at COSY opened a unique possibility to search for the 4He-eta bound state with high statistics and high acceptance. We are conducting a search via an exclusive measurement of the excitation function for the dd -> 3He p pi- reaction.