Some Properties of the Cosmic-Ray Ionizing Particles That Generate Penetrating Showers

Abstract

The mean free path of the ionizing particles that produce penetrating showers has been measured in various materials at 260 and 3260 m above sea level. It has been found that in both places the mean free path is much larger in Pb than in C, and that it increases with the thickness of the absorbers. Possible interpretations are discussed.