Phenomenological analysis of the double-pion production in nucleon-nucleon collisions up to 2.2 GeV

摘要

With an effective Lagrangian approach, we analyze several NN→NNππ channels by including various resonances with mass up to 1.72 GeV. For the channels with the pion pair of isospin zero, we confirm the dominance of N*(1440)→Nσ in the near-threshold region. At higher energies and for channels with the final pion pair of isospin one, we find large contributions from N*(1440)→Δπ, double-Δ, Δ(1600)→N*(1440)π, Δ(1600)→Δπ, and Δ(1620)→Δπ. There are also sizable contributions from Δ→Δπ, Δ→Nπ, N→Δπ, and nucleon pole at energies close to the threshold. We give a good reproduction to the total cross sections up to beam energies of 2.2 GeV except for the pp→ppπ0π0 channel at energies around 1.1 GeV and our results agree with the existing data of differential cross sections of pp→ppπ+π-, pp→nnπ+π+, and pp→ppπ0π0 which are measured at CELSIUS and COSY.