I begin this chapter with the period 1965–1974 when my colleagues and I worked experimentally on the e–μ problem and I became immersed in the then hypothetical world of heavy leptons. I go on to describe the discovery, in the period 1974–1976, of the tau lepton by myself and my colleagues using the SLAC–LBL I detector at the SPEAR e+e− storage ring. I then recount the verification of our discovery by ourselves and others, research that occupied the years 1976 through 1978. In the final section I describe the period 1978–1985, in which the transition was made in experiment and theory to the modern phase of tau research. I have told much of this history in a paper given at the first Workshop on Tau Lepton Physics and so I have repeated here quite a bit of material from that paper. A beautiful description of the discovery of the tau was given recently by Gary Feldman. The discovery of the tau was the subject of a doctoral thesis by Jonathan Treitel at Stanford University.

Before the tau: 1965–1974

The e-μ problem

The history of the discovery of the tau lepton begins in the late 1960s, when my colleagues and I and other experimenters worked on the problem, “How does the muon differ from the electron?” In fact, that was the title of a paper I wrote for Physics Today in 1971.