Roper resonance—Its static and dynamic properties from single- and double-pion production

In most investigations the Roper resonance is sensed only very indirectly via complex partial wave analyses. We find indications for its excitation in the p p → n p π + reaction, where some resonance-like structure is observed in the invariant n π + mass spectrum at M ≈ 1360 MeV with a width of 150 MeV. The values fit very favorably to the most recent phase shift results as well as to the observations at BES. In near-threshold two-pion production p p → p p π 0 π 0 the Roper excitation and its subsequent decay into N π π is the only dominant process. There we find its decay into the N σ channel as the dominating decay process — in favor of a monopole nature of the Roper excitation.