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ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2011, vol. 695, p. 115-123

ΔΔ excitation in proton-proton induced Π0Π0 production

Skorodko T., Bashkanov M., Bogoslawsky D., Calén H., Clement H., Doroshkevich E., Demiroers L., Ekström C., Fransson K., Gustafsson L., Höistad B., Ivanov G., Jacewicz M., Jiganov E., Johansson T., Khakimova O., Keleta S., Koch I., Kren F., Kullander S., Kupsc A., Marciniewski P., Meier R., Morosov B., Pauly C., Petrén H., Petukhov Y., Povtorejko A., Ruber R. J M, Schönning K., Scobel W., Shwartz B., Stepaniak J., Thörngren-Engblom P., Tikhomirov V., Wagner G. J., Wolke M., Yamamoto A., Zabierowski J., Zlomanczuk J.

Exclusive measurements of the pp→ppΠ0Π0 reaction have been performed at CELSIUS/WASA at energies from threshold up to Tp=1.3 GeV. Total and differential cross sections have been obtained. Here we concentrate on energies Tp≥1 GeV, where the ΔΔ excitation becomes the leading process. No evidence is found for a significant ABC effect beyond that given by the conventional t-channel ΔΔ excitation. This holds also for the double-pionic fusion to the quasibound 2He. The data are compared to model predictions, which are based on both Π- and ρ-exchange. Total and differential cross sections are at variance with these predictions and call for a profound modification of the ρ-exchange. A phenomenological modification allowing only a small ρ-exchange contribution leads to a quantitative description of the data. © 2010 Elsevier B.V.