What is the structure of the Roper resonance?

We investigate the structure of the nucleon resonance N∗(1440) (Roper) within a coupled-channel meson exchange model for pion-nucleon scattering. The coupling to ππN states is realized effectively by the coupling to the σN , π∆ and ρN channels. The interaction within and between these channels is derived from an effective Lagrangian based on a chirally symmetric Lagrangian, which is supplemented by well known terms for the coupling of the ∆ isobar, the ω meson and the ’σ’, which is the name given here to the strong correlation of two pions in the scalar-isoscalar channel. In this model the Roper resonance can be described by meson-baryon dynamics alone; no genuine N∗(1440) (3 quark) resonance is needed in order to fit πN phase shifts and inelasticities. PACS:13.75.Gx,14.20.Gk,11.80.Gw,24.10.Eq