Search for Charged Particles with Rest Mass Between that of the Electron and Muon

Abstract

Singly charged particles with rest mass between that of the electron and muon, produced by electro-magnetic pair production, were searched for at the 1-BeV Stanford Electron Accelerator. The experiment had high sensitivity and when combined with theoretical electrodynamics results, rules out the existence of any but very short-lived particles in the range from 1 to $175 m_e$.