Observations on the Tracks of Slow Mesons in Photographic Emulsions

Abstract

Part 2: Origin of the Slow Mesons

IN Part 1 of the present article*, we showed that two types of mesons exist, and it was suggested that the heavier, π-mesons, decay to produce the lighter, μ-mesons. In this second part, we discuss the origin of the slow mesons observed in photographic emulsions, and their relation to the mesons forming the penetrating component of the cosmic rays, of which evidence is provided by experiments with Wilson chambers and counters. We also give photomicrographs which show that some slow mesons, ejected from nuclei during ‘explosive disintegrations’, can enter nuclei and produce a second disintegration. Most of the observations on plates exposed at 5,500 m. were made with boron-loaded emulsions and, for the most part, we have confined our analysis to the results obtained with plates of this type. The loading material has an important influence on the rate of fading of the latent image, but by the above procedure we can compare the results of experiments at different altitudes.