A Cloud-Chamber Investigation of Nuclear Interactions of Cosmic Rays

A magnet cloud chamber recently constructed at Yale University was operated at mountain altitudes (Climax, Colorado, elev. 11 200 feet) during the late fall of 1952. The cloud chamber was electronically controlled to photograph penetrating shower events initiated by high-energy cosmic rays. Five examples of neutral $V$-particle decays have been observed. One photograph reveals the decay of two ${V_2}^0$ particles that probably originated in a single nuclear interaction.