Author/Authors :
Clement، نويسنده , , H. and Bashkanov، نويسنده , , M. and Bargholtz، نويسنده , , C. and Bogoslawsky، نويسنده , , D. and Calen، نويسنده , , H. and Cappellaro، نويسنده , , F. and Demiroers، نويسنده , , L. and Doroshkevich، نويسنده , , E. and Duniec، نويسنده , , D. and Ekstr?m، نويسنده , , Maurice C. R. Franssen، نويسنده , , K. and Gerén، نويسنده , , L. and Gustafsson، نويسنده , , L. and H?istad، نويسنده , , B. and Ivanov، نويسنده , , G. and، نويسنده ,
Abstract :
The ABC effect–an intriguing low-mass enhancement in the π π invariant mass spectrum–is known from inclusive measurements of two-pion production in nuclear fusion reactions. First exclusive measurements carried out at CELSIUS-WASA for the fusion reactions leading to d or 3He reveal this effect to be a σ -channel phenomenon associated with the formation of a Δ Δ system in the intermediate state and combined with a resonance-like behavior in the total cross-section. Together with the observation that the differential distributions do not change in shape over the resonance region the features fulfill the criteria of an isoscalar s-channel resonance in p n and N N π π systems, if the two emitted nucleons are bound. It obviously is robust enough to survive in nuclei as a dibaryonic resonance configuration. In this context also the phenomenon of N Δ resonances is reexamined.
Keywords :
ABC effect , ? channel , ? ? low-mass enhancement , Dibaryonic resonance
