A probable example of the production and decay of a neutral Tau-Meson

Summary  A four-pronged event observed in a magnet cloud chamber is described. It is interpreted as the decay in flight of a neutral π-meson according to the scheme π0 → π +π- + π0 with the subsequent decay of the π0-meson into an electron pair and a γ-ray. The π0-meson is produced in carbon in a small nuclear interaction which may be a charge exchange reaction (K+ + n→π0 + p). The lifetime of the π0-meson before decay is about 3.1010 s. Other possible interpretations of the event are discussed and shown to be improbable.