ISSN - 0217751X, International Journal of Modern Physics A, 2007, vol. 22, p. 509-513
ππ Production in proton-proton collisions
At CELSIUS-WASA the two-pion production in proton-proton collisisons has been measured exclusively from threshold up to the energy regime, where both of the collision partners are expected to be excited to the Δ state. The measurements constitute the first kinematically complete data samples of solid statistics in this energy range. Most of the data have been obtained for the π+π- and π0π0 channels. Whereas at near-threshold energies the differential distributions can be succesfully explained by chiral dynamics and Roper excitation, respectively, the data for the π+π- channel in the ΔΔ region can be described only, if the special configuration (ΔΔ) 0+ is assumed. The data for the π0π0 channel moreover exhibit a low-mass enhancement in the π0π 0 invariant mass spectrum, which is reminiscent of the ABC-effect found in double-pionic fusion to light nuclei. © World Scientific Publishing Company.