The pp→ppπππ 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 160216 MeV. That comprises the first measurement of the pp -> pp pi(0)pi(0)pi(0) reaction and the direct comparison with the pp up arrow pp pi(+)pi(-)pi(0) process. The experiment was performed above the eta meson production threshold and the cross section could be directly normalized to the cross section of the pp -> pp eta reaction, with the eta decaying into 3 pions. Since the same final states are selected, the measurement has a low systematical error. The measured cross section ratio sigma(pp -> pp pi(+)pi(-)pi(0))/sigma(pp -> pp pi(0)pi(0)pi(0)) is compared to predictions of dominance of different isobars in the intermediate state. (c) 2007 Elsevier B.V. All rights reserved.