Murray Gell-Mann (/ˈmʌri ˈɡɛl ˈmæn/; September 15, 1929 – May 24, 2019)[3][4][5][6] was an American theoretical physicist who played a preeminent role in the development of the theory of elementary particles.

Gell-Mann introduced the concept of quarks as the fundamental building blocks of the strongly interacting particles, and the renormalization group as a foundational element of quantum field theory and statistical mechanics.

In the 1970s he was a co-inventor of quantum chromodynamics (QCD) which explains the confinement of quarks in mesons and baryons and forms a large part of the Standard Model of elementary particles and forces.

Unaware of MIT's eminent status in physics research, Gell-Mann was "miserable" with the fact that he would not be able to attend Princeton or Harvard and in characteristic dark irony, said he considered suicide.

[12][13] He received his Ph.D. in physics from MIT in 1951 after completing a doctoral dissertation, titled "Coupling strength and nuclear reactions", under the supervision of Weisskopf.

Gell-Mann spent several periods at CERN, a nuclear research facility in Switzerland, among others as a John Simon Guggenheim Memorial Foundation fellow in 1972.

[37] Although Gell-Mann himself criticized Strange Beauty for some inaccuracies, with one interviewer reporting him wincing at the mention of it, the book was acclaimed by a number of his colleagues.

[41] This work followed the experimental discovery of the violation of parity by Chien-Shiung Wu, as suggested theoretically by Chen-Ning Yang and Tsung-Dao Lee.

[45] Murray Gell-Mann's fortunate encounter with mathematician Richard Earl Block at Caltech, in the fall of 1960, "enlightened" him to introduce a novel classification scheme, in 1961, for hadrons.

[51] In the 1960s, he introduced current algebra as a method of systematically exploiting symmetries to extract predictions from quark models, in the absence of reliable dynamical theory.

This method led to model-independent sum rules confirmed by experiment, and provided starting points underpinning the development of the Standard Model (SM), the widely accepted theory of elementary particles.

[55] Gell-Mann was responsible, with Pierre Ramond and Richard Slansky,[56] and independently of Peter Minkowski, Rabindra Mohapatra, Goran Senjanović, Sheldon Glashow, and Tsutomu Yanagida, for proposing the seesaw theory of neutrino masses.

He is also known to have played a role in keeping string theory alive through the 1970s and early 1980s, supporting that line of research at a time when it was a topic of niche interest.