Electrons associated with negative μ mesons

Abstract

A study has been made in photographic emulsions of low energy electrons associated with stopped negative μ-mesons from the University of Chicago cyclotron. A total of 1000 meson endings has been studied. Of these mesons, 358 decayed into a high energy electron and 32 caused a star. The remaining 610 mesons stopped in the emulsion with no associated tracks other than tracks of low energy electrons (10<E e <100 keV). A low energy electron track is observed from 17 of the−μ-e decays (5 percent). The energy distribution of the low energy electrons from the μ-e decays is consistent with the assumption that the low energy electrons are monoenergetic. The average energy of these electrons is about 17 keV. The low energy electrons are thought to be due to «Auger» transitions of the negative μ-meson from the atomic capture in the light elements of the emulsion. One or more low energy electron tracks are observed from 255 stopped μ-mesons which did not decay or cause a star. These electrons are thought to be due to mesonic «Auger» transitions from the heavy elements in the emulsion. The large difference in the probabilities of electron ejection from the mesonic capture in the light and heavy elements (5 percent as compared to 44 percent) is confirmed by a study of low energy electrons associated with negative μ-meson stars.