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Perl, Martin Lewis

particle electron family physics

(1927– ) US physicist.

Perl grew up in Brooklyn, New York, the son of Jewish immigrants from Poland, and qualified as a chemical engineer at Brooklyn Polytechnic Institute. He worked for GEC on production problems, and left to take a doctoral programme in physics at Columbia in 1950, working on atomic beam resonance to study atomic nuclei under .

Between 1974 and 1977 Perl and colleagues at the Stanford Linear Accelerator Center demonstrated experimentally the existence of the tau lepton, some 3500 times heavier than an electron. This discovery unveiled the third lepton family of fundamental particles, a vital piece of supporting evidence for the theory now known as the Standard Model within particle physics. Before the third family (consisting of the tau particle and its neutrino, v r ) was discovered, theories could not allow charge and parity (CP) violation, which had (most surprisingly) been observed. This asymmetry in our world regulates particle decay and is a very important subtlety in the structure of the universe. Previously only the first family (the electron and electron neutrino) and second family (mu particle and mu neutrino) were known. Corresponding to these six leptons there are six quarks (up and down, charm and strange, and top and bottom for the first to third families respectively). One of the fundamental questions in physics is whether only three families of leptons exist; or will the standard model require revision? Perl received the 1995 Nobel Prize for his discovery, shared with Frederick Reines (1918–98) who had first observed the electron neutrino. He and Clyde Cowan had proposed a reactor experiment to capture neutrinos, as reactors should produce quite intense flows of such particles. Despite the neutrino’s properties making it very difficult to observe, their experiment conclusively demonstrated its presence. This confirmed the vital hypothesis put forward by in 1930, required to explain beta decay (emission of an electron) whilst ensuring conservation of energy. Pauli’s fear had been that his suggested particle might always remain unobservable and place physics in a realm of ongoing speculation.

Perlman, Steve - Overview, Personal Life, Career Details, Chronology: Steve Perlman, Social and Economic Impact [next] [back] Perkins, James, Jr.(1953–) - Mayor, Becomes Politically Active, Chronology, Perkins’ Plans for Selma

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