Search for the double charge exchange reaction in pionic atoms

For some pionic atoms the reaction (π-,π+) is energetically possible. The reaction rate at rest provides information for theoretical explanations of the DCX reaction mechanism between pions and nuclei. Effects of the double isobaric analog states and multi-nucleon processes are involved. The reaction chosen for this experiment was 58Ni(π-,π+)58Fe, the Q-value for this reaction being +903 keV. The experiment was performed, using the large-solid-angle magnetic spectrometer SINDRUM. We conclude that the branching ratio for the DCX reaction has an upper limit of 2.1x10-7 per π- captured from a pionic 58Ni orbit with 90% confidence. (orig.)