I describe the discovery of the tau lepton in the 1970s using the SPEAR electron-positron collider and the SLAC-LBL detector of the Stanford Linear Accelerator Center. I also describe the subsequent verification of the existence of the tau lepton and its leptonic nature by experiments at SPEAR and at the DORIS electron-positron collider at DESY. As a preliminary to the tau discovery I discuss how I became a physicist and became interested in leptons. This history of the discovery of the tau allows me to give a general picture of the high-energy physics world of forty years ago and to discuss the changes that have occurred in the practice of high-energy physics over these forty years.

/pdf/the-discovery-of-the-tau-lepton-and-the-changes-in-3ox51m7s8w.pdf

The Discovery of the Tau Lepton and the Changes in Elementary-Particle Physics in Forty Years

My first thoughts in writing this lecture are about the young women and young men who are beginning their lives in science: students and those beginning scientific research. I have been in experimental scientific research for 45 years; I have done some good experiments of which the best was the discovery of the tau lepton; I have followed research directions that turned out to be uninteresting; I have worked on experiments that failed. And so while recounting the discovery of the tau for which I have received this great honor, I will try to pass on what I have learned about doing experimental science. I begin my reflections by going back in time before the tau, before even my interest in leptons. I was trained as an engineer at Polytechnic University (then the Polytechnic Institute of Brooklyn) and I always begin the design of an experiment with engineering drawings, with engineering calculations on how the apparatus is to be built and how it should work. My strong interest in engineering and in a mechanical view of nature carried over into my career in physics. My doctoral thesis research (Pert, Rabi, and Senitzky 1955) was carried out at Columbia University in the early 1950’s under Professor Isidor Rabi. The research used the atomic beam resonance method invented by Rabi, for which he received a Nobel Prize in 1944. My experimental apparatus, Fig. 1, was boldly mechanical with a brass vacuum chamber, a physical beam of sodium atoms, submarine storage batteries to power the magnets and in the beginning of the experiment, a wall galvanometer to measure the beam current. I developed much of my style in experimental science in the course of this thesis experiment. When designing the experiment and when thinking about the physics, the mechanical view is always dominant in my mind. More important, my thinking about elementary particles is physical and mechanical. In the basic production process for tau leptons

Reflections on the Discovery of the Tau Lepton

The equilibrium properties of a cusp injected, hollow, rotating E layer are self‐consistently calculated by solving the coupled equations representing conservation of energy, canonical angular momentum, and radial force balance. The particles forming the E layer are emitted from an annular knife‐edged cathode, accelerated in the cathode‐anode gap, pass through a cusped magnetic field, and propagate into a coaxial conducting wall system. The steady‐state equilibrium properties including all self‐fields are determined for a given choice of diode parameters, applied cusped magnetic fields, and conducting walls. When only an outer solid conducting wall is considered, a limiting current behavior is observed above a critical magnetic field, whereas, below this critical field, the beam is driven to the wall as the beam intensity increases. When an inner squirrel cage and an outer solid conductor are considered, no limiting current behavior occurs, but the beam is driven to the inner squirrel cage as the beam intensity increases. For this case, equilibria are found to exist above the single particle cutoff field.

Robert A. Mack

Papers

Proceedings of the Sixth International Conference on High Energy Accelerators