Exclusive measurements of pp→dπ+π0: Double-pionic fusion without ABC effect

Exclusive measurements of the reaction pp→dπ+π0 have been carried out at Tp=1.1GeV 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.