Double-Pionic Fusion of Nuclear Systems and the "ABC" Effect: Approaching a Puzzle by Exclusive and Kinematically Complete Measurements
2009 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, no 5, 052301- p.Article in journal (Refereed) Published
The ABC effect-a puzzling low-mass enhancement in the pi pi invariant mass spectrum, first observed by Abashian, Booth, and Crowe-is well known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on the first exclusive and kinematically complete measurements of the most basic double-pionic fusion reaction pn -> d pi(0)pi(0) at beam energies of 1.03 and 1.35 GeV. The measurements, which have been carried out at CELSIUS-WASA, reveal the ABC effect to be a (pi pi)(I=L=0) channel phenomenon associated with both a resonancelike energy dependence in the integral cross section and the formation of a Delta Delta system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data.
Place, publisher, year, edition, pages
2009. Vol. 102, no 5, 052301- p.
IdentifiersURN: urn:nbn:se:uu:diva-137316DOI: 10.1103/PhysRevLett.102.052301ISI: 000263166400020OAI: oai:DiVA.org:uu-137316DiVA: diva2:378030