Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements

M. Bashkanov; C. Bargholtz; M. Berlowski; D. Bogoslawsky; H. Calen; H. Clement; L. Demiroers; E. Doroshkevich; D. Duniec; C. Ekstrom; K. Fransson; L. Geren; L. Gustafsson; B. Hoistad; G. Ivanov; M. Jacewicz; E. Jiganov; T. Johansson; O. Khakimova; S. Keleta; I. Koch; F. Kren; S. Kullander; A. Kupsc; K. Lindberg; P. Marciniewski; R. Meier; B. Morosov; C. Pauly; H. Pettersson; Y. Petukhov; A. Povtorejko; A. Pricking; R. J. M. Y. Ruber; K. Schonning; W. Scobel; B. Shwartz; T. Skorodko; V. Sopov; J. Stepaniak; P. -E. Tegner; P. Thorngren-Engblom; V. Tikhomirov; A. Turowiecki; G. J. Wagner; M. Wolke; J. Zabierowski; I. Zartova; J. Zlomanczuk

doi:10.1103/physrevlett.102.052301

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arXiv · 0806.4942

Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements

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Abstract

The ABC effect - a puzzling low-mass enhancement in the $ππ$ invariant mass spectrum - is well-known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on first exclusive and kinematically complete measurements of the most basic double pionic fusion reaction $pn \to d π^0π^0$ at 1.03 and 1.35 GeV. The measurements, which have been carried out at CELSIUS-WASA, reveal the ABC effect to be a $(ππ)_{I=L=0}$ channel phenomenon associated with both a resonance-like energy dependence in the integral cross section and the formation of a $ΔΔ$ system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data.

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M. Bashkanov, C. Bargholtz, M. Berlowski, D. Bogoslawsky, H. Calen, H. Clement, L. Demiroers, E. Doroshkevich, D. Duniec, C. Ekstrom, K. Fransson, L. Geren, L. Gustafsson, B. Hoistad, G. Ivanov, M. Jacewicz, E. Jiganov, T. Johansson, O. Khakimova, S. Keleta, I. Koch, F. Kren, S. Kullander, A. Kupsc, K. Lindberg, P. Marciniewski, R. Meier, B. Morosov, C. Pauly, H. Pettersson, Y. Petukhov, A. Povtorejko, A. Pricking, R. J. M. Y. Ruber, K. Schonning, W. Scobel, B. Shwartz, T. Skorodko, V. Sopov, J. Stepaniak, P. -E. Tegner, P. Thorngren-Engblom, V. Tikhomirov, A. Turowiecki, G. J. Wagner, M. Wolke, J. Zabierowski, I. Zartova, J. Zlomanczuk. 2009-01-07. Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements. https://doi.org/10.1103/physrevlett.102.052301

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