Cloud-Chamber Study of Collision Electrons in Equilibrium with Mesons

Abstract

A 30-cm counter-controlled Wilson cloud chamber contained a tungsten plate of 3.81-cm thickness. A block of lead either 2.54 or 7.62 cm placed above the cloud chamber enabled a distinction to be made between mesons and electron showers. 601 meson tracks were observed (no magnetic field), 497 of which traversed the tungsten plate. From these, the percentage of fast collision electrons in equilibrium with mesons in tungsten and lead was found to be 10.5 percent and 8 percent, respectively, in good agreement with the theories of Bhabha, and Tamm and Belenky. 143 collision electrons with energy range from 13 kev to 175 kev were produced by meson tracks in the gas and indicated a $\frac{1}{E^2}$ differential spectrum. Some interesting individual events associated with mesons are described.