Low-mass pi pi enhancement in baryonic pi pi production: ABC effect revised by exclusive measurements
2007 (English)In: International Journal of Modern Physics A, ISSN 0217-751X, E-ISSN 1793-656X, Vol. 22, no 2-3, 625-628 p.Article in journal (Refereed) Published
The ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of double-pionic fusion to nuclear bound states - has been investigated since 40 years by inclusive measurements without providing a conclusive interpretation. First exclusive measurements to this topic have now been carried out at CELSIUS-WASA. They confirm a huge ππ threshold enhancement, prove it to be of scalar-isoscalar nature, i.e., a σ-channel phenomenon and reveal the theoretically predicted high-mass enhancement in inclusive spectra to be of πππ rather than of ππ nature - falsifying thus corresponding model predictions for the ABC effect. From the kinematically complete data samples we infer that the interaction between the two Δ particles created in this process is of crucial importance.
Place, publisher, year, edition, pages
2007. Vol. 22, no 2-3, 625-628 p.
ABC effect, σ channel enhancement, ∆∆ interaction, medium effects
IdentifiersURN: urn:nbn:se:uu:diva-16890DOI: 10.1142/S0217751X07035987ISI: 000250926800065OAI: oai:DiVA.org:uu-16890DiVA: diva2:44661