Pionic fusion in light-ion systems

The role of pions in the nuclear interaction has been studied in pionic fusion experiments using the AGOR accelerator facility at KVI. Pionic fusion is a highly coherent process in which two nuclei fuse to a united nucleus and the available centre-of-mass (C.M.) energy is emitted through the pion channel. The examined reactions were 4He(3He, π0)7Be and 6Li(4He, π0)10B⁎ and both reactions were performed at C.M. energies about 10 MeV above the coherent pion production threshold. Here, the experimental results for the 6Li(4He, π0)10B⁎ reaction will be presented and discussed. In order to provide sensitivity to the full dynamics and relevant processes involved in the pionic fusion reaction, almost the full angular distribution of neutral pions has been determined. In a phenomenological analysis, the contributions of Legendre polynomials to reproduce the behaviour of the angular distribution have been studied. The results of this analysis confirm the importance of the clustering correlations for the 6Li(4He, π0)10B⁎ reaction. The mass dependence of the pionic fusion reaction is in agreement with the results of the existing models extrapolated to this reaction.