Richard Henry Dalitz, FRS (28 February 1925 – 13 January 2006) was an Australian physicist known for his work in particle physics. Education and early life Born in the town of Dimboola, Victoria, Dalitz studied physics and mathematics at Melbourne University before moving to the United Kingdom in 1946, to study at the University of Cambridge. His PhD was awarded in 1950 for research on zero-zero transitions in the atomic nucleus supervised by Nicholas Kemmer. Research and career After his PhD, he took up a one-year post at the University of Bristol, and then joined Rudolf Peierls' group at University of Birmingham. Dalitz moved to Cornell University in 1953. He then became a professor at the Enrico Fermi Institute in Chicago from 1956 to 1963. Next, he moved to the University of Oxford as a Royal Society research professor, although keeping a connection with Chicago until 1966. He retired in 1990. At Birmingham he completed his thesis demonstrating that the electrically neutral pion could decay into a photon and an electron-positron pair, now known as a Dalitz pair. In addition, he is known for other key developments in particle physics: the Dalitz plot and the Castillejo–Dalitz–Dyson (CDD) poles. The Dalitz plots were discovered in 1953, while he was at Cornell. Dalitz plots play a central role in the discovery of new particles in current high-energy physics experiments, including Higgs boson research, and are tools in exploratory efforts that might open avenues beyond the standard model. His various fundamental contributions have led to practitioners in the field to identify Dalitz as one of particle physics "greatest unsung scientists" and "a theorist exceptionally valued by experimentalists." Quantum mechanics Dalitz was an old and close friend of John Clive Ward, the creator of the Ward Identities. Their friendship began around 1948 when Dalitz independently derived Ward's results for the polarisation entanglement of two photons propagating in opposite directions. Dalitz was the lead author of a succinct, and yet revealing, account of Ward's physics. While commenting on the physics surrounding the derivation of the probability amplitude by Ward, Dalitz and Duarte wrote: "Ward and Pryce calculated, using quantum mechanics, the distribution of the azimuth angle between the planes of polarization of... two gamma rays from positron-electron annihilation... the two photons are entangled and according to local realism, their polarization planes should become independent... a typical EPR situation. Already in 1948, observations... agreed with quantum