Kenneth Marshall Watson (born 7.09.1921) is an American theoretical physicist and a member of the National Academy of Sciences (1974). He graduated from Iowa State College (1943). In 1948-49 he worked at the Institute for Advanced Study in Princeton, in 1951 —53 at Indiana University and in 1953 —57 at the University of Wisconsin. From 1957 he was professor at the University of California at Berkeley.
His research concerned nuclear physics, the theory of scattering and the physics of elementary particles. Together with K. Brueckner he extended (1952) the theory of the photoproduction of mesons, and he proposed (1953) an effective method of solving scattering problems which has a certain connection with the Tamm–Dancoff approximation. He was the first to investigate (1951) the important part played by isotopic spin in the production of a meson. He developed a phenomenological theory of the scattering of pions by protons, and studied various aspects of nuclear forces, in particular the scattering of virtual mesons by two interacting nucleons. In 1954, with M. Gell-Mann, he constructed a theory of the photoproduction of mesons in which the photoproduction cross-section is expressed in terms of the matrix elements of electric and magnetic multipole transitions, and he later developed it further himself (the Watson theory).