engleski

Pionic fusion experiments at KVI

Two experiments aiming to study pionic fusion of light nuclei were performed using the AGOR accelerator facility. In such reactions a pion and a fused nucleus are produced in a collision of two nuclei. The examined reactions are 4He(3He, pi0)7Be and 6Li(4He, pi0)10B at beam energies about 10 MeV above the coherent pion production threshold (261 MeV and 234 MeV). Since the energy is well below the pion production threshold in an elementary nucleon-nucleon process a highly coherent mechanisms is needed (1). Produced nuclei were detected and identified in a phoswich detector array in the focal plane of the BBS spectometer (2) and photons originating from pion decay in the Plastic Ball detector (3). The Plastic Ball contains 552 phoswich modules covering polar laboratory angles between 60 and 160 degrees in almost the full azimuthal range. It is equipped with an inner shell of 64 CsI crystals in order to improve photon conversion. The results of the ongoing analyses of the first reaction will be presented. Approximately 700 good events fulfilling the kinematical condition for an outgoing 7Be and a pi0 decaying with large opening angle have been selected. The angular distribution of neutral pions will be discussed. (1)T. Kajino. H. Toki and K. Kubo, Phys. rev. C35, 1370 (1987) (2) A.M. van der Berg, Nucl. Instr. and Meth. B99, 637 (1995) (3) A. Baden et al., Nucl. Instr. and Meth. 203, 189 (1982)

pionic fusion; cluster; Plastic Ball

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