Coupled channels approach to ηN and η′N interactions

Abstract

We present a coupled channels separable potential approach to ηN and η′N interactions using a chiral-symmetric interaction kernel. The s-wave πN amplitudes and π−p induced total cross sections are reproduced satisfactorily in a broad interval of energies despite limiting the channel space to two-body interactions of pseudoscalar mesons with the baryon ground-state octet. It is demonstrated that an explicit inclusion of the η0 meson singlet field leads to a more attractive ηN interaction, with the real part of the scattering length exceeding 1 fm. The η′N diagonal coupling appears sufficient to generate an η′N bound state but the inter-channel dynamics moves the respective pole far from the physical region making the η′N interaction repulsive at energies around the channel threshold. The N⁎(1535) and N⁎(1650) resonances are generated dynamically and the origin and properties of the S-matrix poles assigned to them are studied in detail. We also hint at a chance that the N⁎(1895) state might also be formed provided a suitably varied model setting is found.