Particles In Extensive Air Showers Research Articles

Penetrating Particles in Extensive Cosmic-Ray Air Showers

The number of penetrating particles in extensive air showers has been determined as a function of range of the particles and size of the showers at 3260-m elevation. A measurement with the same apparatus has been made at 260-m elevation, in order to show the altitude variation. It is found that the showers at 3260 m contain many photons and electrons which can be detected under absorbers up to 7-inches lead. The particles penetrating more than this thickness have a very small absorption coefficient in iron, and decrease in density slowly as they traverse the atmosphere. Hence they are thought to be primarily $\ensuremath{\mu}$-mesons.

Penetrating Particles in Extensive Air Showers

Penetrating particles in extensive air showers have been studied at 4300- and 3260-m elevations. The particles capable of penetrating 14 cm lead are about 1 per 30 shower particles at 3260 m and 1 per 25 at 4300 m. The number of penetrating particles is reduced by a factor 1.8 when the lead is increased from 15.5 to 39 cm, and the density of the penetrating particles diminishes by a factor 1.7 between 4300 and 3260 m elevation. These facts imply the penetrating particles are very numerous and have too low average energy to be mesons coming from the top of the atmosphere. Further experiments show that they are not produced multiply in lead shields above the counters. This fact, together with the independence of their number on the atomic number of the absorber, seems to indicate they are not produced by photons.

Production of penetrating particles in extensive air showers

The present paper contains an analysis of the experimental material presented in two previous communications (Broadbent & Jánossy 1947 a,b , referred to as I and II) and also the important papers of Cocconi, Loverdo & Tongiorgi (1943, 1944, 1946 a,b ), and those of Daudin (1942, 1943). Use is also made of unpublished experimental material obtained by Miss B. Choudhuri.