ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2007, vol. 649, p. 122-127
The p p → p p π π π reaction channels in the threshold region
The cross section for direct neutral and charged three pion production in pp interactions was measured at excess energies in the range 160-216 MeV. That comprises the first measurement of the p p → p p π0 π0 π0 reaction and the direct comparison with the p p → p p π+ π- π0 process. The experiment was performed above the η meson production threshold and the cross section could be directly normalized to the cross section of the p p → p p η reaction, with the η decaying into 3 pions. Since the same final states are selected, the measurement has a low systematical error. The measured cross section ratio σ (p p → p p π+ π- π0) / σ (p p → p p π0 π0 π0) is compared to predictions of dominance of different isobars in the intermediate state. © 2007 Elsevier B.V. All rights reserved.