A Hodoscope Study of Penetrating Cosmic-Ray Showers. II. Extensive Showers

The interactions of penetrating particles in air showers have been studied with a hodoscope arrangement at an altitude of 3260 m. About 90 percent of all charged penetrating particles do not originate local showers of penetrating secondaries, and are absorbed only very slowly. This "non-interacting component," consisting at least predominantly of μ-mesons, has a rather flat range spectrum between 280 and 680 g/cm² Pb. Its zenith angle distribution is approximately, proportional to cos⁴θ. The remaining 10 percent constitute a "charged N component"; the total fast N component amounts to about one-fourth of the number of the charged penetrating particles. The collision mean free path of the fast N component was found to be (220±{}30) g/cm² if a minimum of 100-g/cm² penetration is demanded for the local showers. From the recorded increase of the number of shower particles with absorber thickness it is concluded that further multiplication after the first collision is quite common, and that the mean free path of the secondaries of local showers is not much larger than that of the primary N component.