Observation of the abc effect in the first exclusive measurements of pn -> d pi(0)pi(0)
2007 (English)In: International Journal of Modern Physics A, ISSN 0217-751X, E-ISSN 1793-656X, Vol. 22, no 2-3, 617-620 p.Article in journal (Refereed) Published
The reaction pn → dπ0π0 constitutes the most fundamental system for the study of the ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of the ππ system in double-pionic fusion to nuclear bound states. The first exclusive measurements of this reaction have now been carried out at CELSIUS-WASA. They exhibit a striking low-mass enhancement in the ππ invariant mass spectrum, prove it to be a σ-channel phenomenon and falsify conventional theoretical models, which predict an associated high-mass enhancement not present in the new exclusive data. In the kinematically complete data sample we observe a ΔΔ excitation, where the interaction between the two Δ obviously plays a crucial role for the generation of the ππ low-mass enhancement.
Place, publisher, year, edition, pages
2007. Vol. 22, no 2-3, 617-620 p.
ABC effect, σ channel enhancement, ΔΔ interaction, medium effects
IdentifiersURN: urn:nbn:se:uu:diva-16891DOI: 10.1142/S0217751X07035963ISI: 000250926800063OAI: oai:DiVA.org:uu-16891DiVA: diva2:44662