Mixed Cosmic-Ray Showers at Sea Level

Abstract

A detailed analysis of 15 cloud-chamber photographs of mixed showers is given. This analysis gives the following results: (a) Mixed showers contain, in general, both slow and fast heavy particles in addition to the electron component. Some of the heavy particles can be identified as protons and some as mesons. (b) The electron component of the mixed showers consists sometimes of a single cascade shower and sometimes of several cascade showers. In cases where only a single cascade shower is present its axis is found to be within an angle of 2 or 3 degrees from the direction of the primary particle when this is observable. In cases where several cascade showers appear, one of them often propagates nearly in the direction of the primary particle when this is observable. (c) The simultaneous existence of several cascade showers with their axes diverging at fairly large angles indicates that several high energy electrons or photons are produced in the shower origin. (d) In three cases, an electron group is produced below the shower origin by a non-ionizing particle which seems to originate from the primary nuclear event. These particles may be photons. (e) In one case, two successive nuclear events are observed, which are separated by approximately 60 g/${\mathrm{cm}}^2$ of lead. (f) In one case, a star is produced by a penetrating shower particle after traversing approximately 30 g/${\mathrm{cm}}^2$ of lead.