Martin Lewis Perl
Perl, Martin Lewis (1927-) is an American physicist who 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 American physicist Frederick Reines for detection of the neutrino, another type of lepton.
Perl was born in New York City on June 24, 1927. His parents, Oscar Perl and Fay Rosenthal Perl, were immigrants from Russia who established a printing company in New York. Perl graduated in chemical engineering from Polytechnic Institute of Brooklyn (now Polytechnic University). He obtained a Ph.D. degree in physics from Columbia University in 1955. His supervisor was the 1944 Nobel physicist Isidor Isaac Rabi, who encouraged Perl to study subatomic particles. In 1963, Perl began working at the Stanford Linear Accelerator Center (SLAC), where a giant particle accelerator was soon built, at Stanford University, in Stanford, California. He was appointed professor of physics and chair of the High Energy Physics Faculty at the SLAC
Perl worked with Stanford Positron-Electron Asymmetric Ring (SPEAR), 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. The other two families of elementary particles are quarks and fundamental bosons. Perl's new particle 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 is a member of the National Academy of Sciences and a fellow of the American Physical Society.