Gell-Mann, Murray (1929– )

US theoretical physicist. In 1964 he formulated the theory of the quark as one of the fundamental constituents of matter. He was awarded the Nobel Prize for Physics in 1969 for his work on elementary particles and their interaction.

Gell-Mann proposed a classification system for elementary particles in 1962, called the eightfold way. It postulated the existence of supermultiplets, or groups of eight particles which have the same spin value but different values for charge, isotopic spin, mass, and strangeness. The model also predicted the existence of supermultiplets of different sizes.

Gell-Mann was born in New York and studied at Yale and the Massachusetts Institute of Technology. He became professor at the California Institute of Technology in 1956.

Gell-Mann proposed in 1953 a new quantum number called the strangeness number, together with the law of conservation of strangeness, which states that the total strangeness must be conserved on both sides of an equation describing a strong or an electromagnetic interaction but not a weak interaction. This led to his theory of associated production in 1955 concerning the creation of strange particles. Gell-Mann used these rules to group mesons, nucleons (neutrons and protons), and hyperons, and was thereby able to form successful predictions.