Emilio Segrè
1905–1989, Tivoli, Italy, Lafayette, California
Italian-American physicist who, with Owen Chamberlain, discovered the antiproton and won the 1959 Nobel Prize in Physics.
Born in Tivoli, Segrè was a student of Enrico Fermi in Rome, part of the group that discovered slow neutrons, and co-discoverer of the first artificial element, technetium (1937), as well as astatine (1940). Driven from Italy by the fascist racial laws of 1938, he settled in the United States and worked at Berkeley.
During the Second World War he joined the Manhattan Project at Los Alamos, where his group showed that reactor-produced plutonium-239 could not be used in a gun-type bomb because of plutonium-240. After the war he returned to Berkeley and led the team that discovered the antiproton in 1955.
Nobel-winning work
In 1955, Segrè's team at Berkeley's Bevatron fired protons of about 6 GeV onto a copper target — above the 5.6 GeV threshold needed to produce a proton–antiproton pair. The challenge was picking out the rare antiprotons among tens of thousands of background particles.
The group combined scintillation counters and velocity-selecting Cherenkov detectors to measure the velocity and mass of each particle simultaneously: events passing the system behaved exactly as expected for a proton-mass particle of negative charge. The announcement of the antiproton — published in Physical Review in 1955 — confirmed Dirac's antimatter prediction for the proton and opened the era of antiparticle physics.
Workplaces: University of California, Berkeley, University of Rome
United States, Italy