The ABC Effect and its Energy Dependence in the Double-Pionic Fusion to 4He
2011 (English)In: International Journal of Modern Physics A, ISSN 0217-751X, E-ISSN 1793-656X, Vol. 26, no 3-4, 699-701 p.Article in journal (Refereed) Published
The double-pionic fusion reactions dd → 4Heπ0π0 and dd → 4Heπ+π- were measured exclusively and kinematically complete with the WASA detector at COSY. The measurements were performed in the energy range Tp = 0.8 - 1.4 GeV covering thus the full energy region, where the so-called ABC effect – a peculiar low-mass enhancement in the ππ-invariant mass spectrum – was observed previously in inclusive measurements. Our findings for the double-pionic fusion to 4He are in accordance with the observations for the basic pn → dπ0π0 reaction pointing to the same fundamental mechanism. In both cases we observe that the ABC effect is associated with a peak in the energy dependence of the total cross section. In the 4He case the peak structure in the total cross section is broadened in comparison to the deuteron case. This is consistent with both Fermi motion of the basic pn system within 4He and with collision broadening as it is known, e.g., from excitations of the Δ resonance in nuclei.
Place, publisher, year, edition, pages
2011. Vol. 26, no 3-4, 699-701 p.
IdentifiersURN: urn:nbn:se:uu:diva-170917DOI: 10.1142/S0217751X11052578ISI: 000287529800096OAI: oai:DiVA.org:uu-170917DiVA: diva2:509740
WASA at COSY collaboration2012-03-132012-03-132012-10-24Bibliographically approved