Martin Perl and the Tau Lepton
‘Martin L. Perl, a professor at the Stanford Linear Accelerator Center (SLAC), [was] awarded the 1995 Nobel Prize in physics ... for his 1975 discovery of a new elementary particle known as the tau lepton. ... The tau lepton is a superheavy cousin of the electron, the carrier of electrical current in household appliances. The two particles are identical in all respects except that the tau is more than 3,500 times heavier than the electron and survives less than a trillionth of a second, whereas the electron is stable.
In the mid-1970s, working at the Stanford Positron-Electron Asymmetric Ring (SPEAR) in collaboration with 30 other physicists from SLAC and Lawrence Berkeley National Laboratory, Perl began to find events recorded by the detector that could not be explained by any of the known subatomic particles. After more than a year of analysis, Perl was able to convince the rest of his research team that they were in fact observing a new and different type of elementary particle, which he named the 'tau'.
In the standard model of particle physics, the elementary building blocks of matter appear in families, with two leptons and two quarks in each. Until Perl's discovery there were only two such families known to exist.
The tau turned out to be the first-discovered member of a third quark-lepton family. In 1976, the second particle in the family, the bottom quark, was discovered by scientists at Fermi National Accelerator Laboratory. It was not until 1995 that Fermi scientists discovered the third member, the top quark.
Addressing the question of the usefulness of the discoveries like that of the tau lepton, Perl said, "The use of the discovery of basic particles is indirect. We have found that everything of a complicated nature is made from three basic families of particles. Eventually, this will lead to an improved understanding of energy and time. From that we hope will come new ideas that lead to applications like a source of cheap energy which is truly safe."
Perl received his Ph.D. in 1955 from Columbia University ... [and] has been on the faculty at SLAC since 1963.'
Additional information about Martin Perl and his research is available in full-text and on the Web.
The Discovery of the Tau Lepton: Part 1, the Early History Through 1975; Part 2, Confirmation of the Discovery and Measurement of Major Properties, 1976--1982, DOE Technical Report, 1994
The Discovery of the Tau and Its Major Properties: 1970--1985, DOE Technical Report, 1990
Status of Heavy-lepton Searches, DOE Technical Report, 1981
The Tau Lepton, DOE Technical Report, 1979
Review of Heavy Lepton Production in e+e- Annihilation, DOE Technical Report, 1977
Threshold and Other Properties of U Particle Production in e+e- Annihilation, DOE Technical Report, 1976
Additional Web Pages:
’55 Grad Wins Physics Prize ..., Columbia University
Physics Nobel Awarded to Martin Perl, The Interaction Point
Interview with Martin L. Perl, August 27, 2008, nopelprize.org (video)
Martin L. Perl, Winner of 1995 Nobel Prize for Discovery of Tau Lepton, Dead at 87