Resonances of the NN̄ system within a field theoretical model

The bound resonance states of the NN? system are calculated on the basis of the OBE model for nuclear forces. The widths of these states are for the first time calculated microscopically in as much as the corresponding bloc diagrams for the decay in two bosons are treated explicitly. All parameters of the boson-nucleon coupling scheme were determined from a fitting of the OBEP to the experimental NN scattering phases. In contrast to former treatments (introduction of a phenomenological imaginary part of the potential) three narrow bound states (among a large number of very broad unobservable levels) were found with level widths smaller than 30 MeV. Levels of this kind were suggested by earlier experiments which, however, were not confirmed by later investigations.