ISSN - 14346001, EISSN - 1434601X, European Physical Journal A, 2008, vol. 35, p. 317-319
Excitation of the Roper resonance in single- and double-pion production in nucleon-nucleon collisions
In most investigations the Roper resonance is sensed only very indirectly via complex partial-wave analyses. We find indications for its excitation in the invariant nπ+ mass spectrum of the pp → npπ+ reaction 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 the near-threshold two-pion production pp → ppπ 0π0 , where the Roper excitation and its subsequent decays via the routes N * → Δπ → Nππ and N * → Nσ are the only dominant processes, we find its direct decay into the Nσ channel to be the by far dominating decay process - in favor of a monopole excitation of the Roper resonance. © 2008 Società Italiana di Fisica and Springer-Verlag.