Pionic fusion Experiments at subthreshold energies

In order to study the role of pions and clustering phenomena in nuclei, two experiments have been performed using the AGOR accelerator facility. In collisions of two nuclei a pion and a fused nucleus were produced. The examined reactions were He-4(He-3, pi(0))Be-7 and Li-6(He-4, pi(0)) B-10 at beam energies about 10 MeV above the coherent pion production threshold (256 MeV and 236.4 MeV, respectively). Since the available energy is well below the pion production threshold in an elementary nucleon-nucleon process, a highly coherent mechanism is needed. We identified the reaction by measuring the fused system in the magnetic spectrometer and the produced neutral pions in the Plastic Ball detection system with large acceptance. Our experimental setup provided the exclusive cross sections by identifying all products in overdetermined kinematics. Here we present the preliminary results of die ongoing analysis for the second reaction. About 700 events fulfilling the kinematical conditions for an outgoing B-10 and a pi(0) decaying with large opening angle have been selected. Angular distribution of neutral pions will be discussed.