Production ofΛ0Particles in Lead and Carbon by 2.5-Bev Protons

In a systematic study of 18 000 pictures taken at the Cosmotron with the Yale diffusion cloud chamber, two ${\Lambda }^0$ decays were found having origin in a lead plate at the upstream edge of the chamber. With corrections for the geometric efficiency of the chamber and for the scanning efficiency, this leads to an upper limit of approximately 8 mb per lead nucleus for the production of ${\Lambda }^0$ particles.