Exclusive measurement of two-pion production in the dd -> He-4 pi pi reaction
2009 (English)In: Nuclear Physics A, ISSN 0375-9474, Vol. 825, no 1-2, 71-90 p.Article in journal (Refereed) Published
The results from the first kinematically complete measurement of the dd -> He-4 pi pi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar pi pi-invariant mass distributions appearing in double pion production in light ion collisions, the so-called ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV. with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low pi pi-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, Our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN -> d pi sub-processes. (C) 2009 Elsevier B.V. All rights reserved.
Place, publisher, year, edition, pages
2009. Vol. 825, no 1-2, 71-90 p.
NUCLEAR REACTIONS 2H(d, 2 pi 0), (d, pi plus pi-), E=712, 1029 MeV, measured sigma(theta), invariant mass spectra, energy spectra and other reaction observables, Comparison with simplified Delta Delta model and earlier results
IdentifiersURN: urn:nbn:se:uu:diva-128410DOI: 10.1016/j.nuclphysa.2009.04.008ISI: 000267188500004OAI: oai:DiVA.org:uu-128410DiVA: diva2:331566