Richard Henry Dalitz (born 28.02.1925) is an English theoretical physicist and a Fellow of the Royal Society (1960). He was born in Dimboola (Australia). He graduated from the University of Melbourne (1946) and in 1950 received his doctorate at the University of Cambridge. In 1951—56 he worked at the universities of Birmingham, Cornell and Stanford, at the Institute for Advanced Study in Princeton and at Brookhaven National Laboratory, and in 1956—66 at the E. Fermi Institute for Nuclear Studies (Chicago). From 1963 he has been professor at the University of Oxford.
His research was in the field of nuclear physics and the physics of elementary particles (the decay of mesons and baryons, the nuclear interactions of the lambda hyperon, models of elementary particles). He calculated (1951) the radiative corrections for internal pair production and constructed a phenomenological theory of hypernuclei. He was one of the first to give a calculation of the electroproduction of pions. He calculated the probability of the decay of π0 into an electron-positron pair and a gamma quantum. He developed (1953) diagrams for the analysis of three-particle resonant states (the Dalitz plot). He was the first to formulate the τ–θ paradox clearly.
The Hughes Medal (1975) and the R. Oppenheimer Prize (1980).