Quark
The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964. Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until deep inelastic scattering experiments at the Stanford Linear Accelerator Center in 1968. Accelerator experiments have provided evidence for all six flavors. The top quark, first observed at Fermilab in 1995, was the last to be discovered.
George Zweig
George Zweig (; born May 30, 1937) is a Russian-American physicist. He was trained as a particle physicist under Richard Feynman. He introduced, independently of Murray Gell-Mann, the quark model (although he named it "aces"). He later turned his attention to neurobiology. He has worked as a Research Scientist at Los Alamos National Laboratory and MIT, and in the financial services industry.