Production of Mesons by the 184-Inch Berkeley Cyclotron

The authors have observed tracks which they believe to be due to mesons in photographic plates placed near a target bombarded by 380 Mev alpha particles. For a 10-minute exposure in the cyclotron, about 50 meson tracks are found along the 3-inch edge of a photographic plate. The mass has been determined by measuring the bending in the magnetic field and the range in emulsion. From the first 50 meson tracks measured they find a mass of 313 {+-} 16 electron masses. It is highly probable that these mesons are the heavy mesons described by Lattes, Occhialini, and Powell.