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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

Pauly C., Jacewicz M., Koch I., Bashkanov M., Bogoslawsky D., Calén H., Capellaro F., Clement H., Demirörs L., Ekström C., Fransson K., Gustafsson L., Höistad B., Ivanov G., Jiganov E., Johansson T., Keleta S., Kullander S., Kupść A., Kuznetsov A., Marciniewski P., Meier R., Morosov B., Oelert W., Petukhov Y., Pettersson H., Povtorejko A., Ruber R. J M Y, Schönning K., Scobel W., Skorodko T., Shwartz B., Sopov V., Stepaniak J., Tchernyshev V., Thörngren Engblom P., Tikhomirov V., Turowiecki A., Wagner G. J., Wiedner U., Wolke M., Yamamoto A., Zabierowski J., Złomańczuk J.

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.