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
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.