Discovery of eta-mesic nuclei

Abstract

First experimental results from a photoreaction which confirm an existence of eta-mesic nuclei are discussed. The experiment was performed at the 1 GeV electron synchrotron of LPI. Two values of the end-point energy of the bremsstrahlung beam were used, 650 and 850 MeV (below and above eta-photoproduction threshold on the nucleon). Correlated pi+ n pairs flying from the 12C target were detected by two TOF scintillator spectrometers placed in opposite directions and transversely to the gamma beam. Measured energy spectra provide a strong evidence for a creation of eta-mesic nuclei as intermediate states of the reaction studied.