ISSN - 14346001, EISSN - 1434601X, European Physical Journal A, 2011, vol. 47, p. 108-
Exclusive measurement of the pp → nnπ +π + reaction at 1.1 GeV
First exclusive data for the pp → nnπ +π + reaction have been obtained at CELSIUS with the WASA detector setup at a beam energy of T p = 1.1 GeV. Total and differential cross-sections disagree with theoretical calculations, which predict the ΔΔ excitation to be the dominant process at this beam energy. Instead, the data require the excitation of one of the nucleons to a higher-lying Δ state, preferably the Δ(1600)P 33, to be the leading process. © The Author(s) 2011.