This week would have marked the 94th birthday of physicist Emilio Segrè, discoverer of the antiproton. The Italian-born American physicist, who died in 1989, studied proton-proton and proton-neutron interactions at the cyclotron accelerator in Berkeley, California. In the early 1950s, Segrè used the Bevatron to accelerate protons to 6 billion electron volts and smash them into a metal plate. The collisions yielded a negatively charged beam composed mainly of pions, muons, and electrons. Segrè also detected in the beam the faint presence of antiprotons--a discovery that earned him and colleague Owen Chamberlain the 1959 Nobel Prize in physics. The existence of antiprotons had been predicted 20 years earlier by physicist Paul Dirac.
[Source: Roy Porter, Ed., The Biographical Dictionary of Scientists (Oxford University Press, ed. 2, 1994).]