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ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2010, vol. 684, p. 110-113

Exclusive measurements of p p → d π+ π0: Double-pionic fusion without ABC effect

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

Exclusive measurements of the reaction p p → d π+ π0 have been carried out at Tp = 1.1   GeV at the CELSIUS storage ring using the WASA detector. The isovector π+ π0 channel exhibits no enhancement at low invariant ππ masses, i.e. no ABC effect. Therefore this most basic isovector double-pionic fusion reaction qualifies as an ideal test case for the conventional t-channel ΔΔ excitation process. Indeed, the obtained differential distributions reveal the conventional t-channel ΔΔ mechanism as the appropriate reaction process, which also accounts for the observed energy dependence of the total cross section. © 2010 Elsevier B.V. All rights reserved.