A Study of Penetrating Showers at 3260 Meters

A series of experiments on local penetrating showers is described. Neon bulbs electronically connected to Geiger counters were lighted and photographed when those counters were struck in a simple coincidence. One row of counters recorded delayed coincidences. Most of the experiments described were performed at Echo Lake, Colorado, elevation 3250 meters.The experiments indicate that there are approximately equal numbers of charged and neutral primary particles. The measured mean free path is found to decrease with increasing energy. The charged primary particles are shown to have a very strong zenith angle dependence.Properties of the secondary particles of the showers were also studied. A large fraction of the penetrating particles locally produced are shown to be mesons. Of all the mesons that stop and decay in the apparatus, apparently about 16 percent are locally produced in penetrating showers. There are many short range particles produced that are not measons. The angular distribution of the penetrating secondaries about the shower axis shows a strong concentration of the particles in the forward direction, such that they could not be emitted symmetrically in the center of gravity system.