The Discovery of the Tau Lepton*

The discovery of the tau lepton and the third generation of fermions came from the convergence of three physics streams in the late 1960’s and early 1970’s. These streams were: the failed attempts by myself and others to understand the connection between the electron and the muon, the development of electron-positron storage rings, and the development of the theory of sequential leptons. In this paper I give the history of the discovery of the tau and the measurement of its major properties-the properties which established the tau as a sequential lepton. Presented at the Third International Symposium on the History of Particle Physics: The Rise of the Standard Model, Stanford, CA, June 24-27,1992 * This work was supported by the Department of Energy, contract DE-AC03-76SF00515. .I