Perl, Martin Lewis (1927-2014), an American physicist, discovered a subatomic particle called the tau lepton, the first known example of the lepton family of particles. In 1995, he received half of the Nobel Prize in physics for this work. The other half was awarded to fellow American Frederick Reines for detection of the neutrino, another type of lepton.
Perl worked with SPEAR (Stanford Positron-Electron Asymmetric Ring), a machine that hurls electrons and positrons (positively charged anti-electrons) at each other. In 1975, Perl announced that he had found evidence of a new kind of particle being produced. The particle had nearly twice the mass of a proton, and rapidly broke down to produce electrons, positrons, and neutrinos. Eventually the physics community became convinced that this new particle belonged to a third family of particles. It was named the tau lepton, or simply tau. Later, the other particles belonging to the third family of matter were discovered—the tau-neutrino and the top and bottom quark.
Perl was born in New York City on June 24, 1927. He graduated in chemical engineering from the Polytechnic Institute of New York (now the New York University Tandon School of Engineering). From 1948 until 1950, Perl worked for the General Electric Company. He then went to Columbia University and obtained a Ph.D. in physics in 1955. His supervisor, the great physicist Isidor Isaac Rabi, encouraged him to study subatomic particles. Perl went on to do research in this field at the University of Michigan. In 1963, he went to the Stanford Linear Accelerator Center (SLAC), which had a giant particle accelerator. Perl died on Sept. 30, 2014.
