A Doubly Charged Cosmic Ray Particle

Abstract

AMONG more than a thousand stereoscopic counter-controlled cloud chamber photographs of mesons which we have obtained during the past six months while studying the scattering of mesons of different energies in lead plates, we have obtained the photograph reproduced herewith. Each one of the stereoscopic cameras made an angle of 22½° with the normal to the chamber. The chamber was triggered by a triple coincidence Geiger – Muller counter system with 25 cm. of lead below the chamber and above the lowest counter, so at least one of the particles must penetrate 25 cm. of lead. There was no lead on the top of the chamber. The usual argon–alcohol mixture was used in the chamber.