Richard Henry Dalitz, FRS (28 February 1925 – 13 January 2006) was an Australian

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

known for his work in

particle physics Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...

Education and early life

Born in the town of

Dimboola Dimboola is a town in the Shire of Hindmarsh in the Wimmera region of western Victoria, Australia, 334 kilometres north-west of Melbourne. History Situated on the Wimmera River, Dimboola was previously known as 'Nine Creeks'. Following a survey ...

, Victoria, Dalitz studied physics and mathematics at

Melbourne University The University of Melbourne (colloquially known as Melbourne University) is a public research university located in Melbourne, Australia. Founded in 1853, it is Australia's second oldest university and the oldest in the state of Victoria. Its ...

before moving to the United Kingdom in 1946, to study at the

University of Cambridge The University of Cambridge is a Public university, public collegiate university, collegiate research university in Cambridge, England. Founded in 1209, the University of Cambridge is the List of oldest universities in continuous operation, wo ...

. His

PhD A Doctor of Philosophy (PhD, DPhil; or ) is a terminal degree that usually denotes the highest level of academic achievement in a given discipline and is awarded following a course of graduate study and original research. The name of the deg ...

was awarded in 1950 for research on zero-zero transitions in the

atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the Department_of_Physics_and_Astronomy,_University_of_Manchester , University of Manchester ...

supervised by

Nicholas Kemmer Nicholas Kemmer (7 December 1911 – 21 October 1998) was a Russian-born nuclear physics, nuclear physicist working in Britain, who played an integral and leading edge role in United Kingdom's British nuclear weapons, nuclear programme, and was ...

Research and career

After his PhD, he took up a one-year post at the

University of Bristol The University of Bristol is a public university, public research university in Bristol, England. It received its royal charter in 1909, although it can trace its roots to a Merchant Venturers' school founded in 1595 and University College, Br ...

, and then joined

Rudolf Peierls Sir Rudolf Ernst Peierls, (; ; 5 June 1907 – 19 September 1995) was a German-born British physicist who played a major role in Tube Alloys, Britain's nuclear weapon programme, as well as the subsequent Manhattan Project, the combined Allied ...

' group at

University of Birmingham The University of Birmingham (informally Birmingham University) is a Public university, public research university in Birmingham, England. It received its royal charter in 1900 as a successor to Queen's College, Birmingham (founded in 1825 as ...

. Dalitz moved to

Cornell University Cornell University is a Private university, private Ivy League research university based in Ithaca, New York, United States. The university was co-founded by American philanthropist Ezra Cornell and historian and educator Andrew Dickson W ...

in 1953. He then became a professor at the

Enrico Fermi Institute __NOTOC__ The Institute for Nuclear Studies was founded September 1945 as part of the University of Chicago with Samuel King Allison as director. On November 20, 1955, it was renamed The Enrico Fermi Institute for Nuclear Studies. The name was ...

in Chicago from 1956 to 1963. Next, he moved to the

University of Oxford The University of Oxford is a collegiate university, collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the List of oldest un ...

as a

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

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 proposed 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 The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...

. 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 John Clive Ward, (1 August 1924 – 6 May 2000) was an Anglo-Australian physicist who made significant contributions to quantum field theory, condensed-matter physics, and statistical mechanics. Andrei Sakharov called Ward one of the titans o ...

, the creator of the

Ward Identities Ward may refer to: Division or unit * Hospital ward, a hospital division, floor, or room set aside for a particular class or group of patients, for example the psychiatric ward * Prison ward, a division of a penal institution such as a pris ...

. 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 :

\left, \psi\right\rang=(\left, x,y\right\rang - \left, y,x\right\rang )

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 mechanics, not with ''local realism''."

Quarks

Dalitz was directly involved in pioneering quark research since the early 1960s, at a time when leading theorists considered quarks as purely mathematical entities, and he participated in the identification of the top

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nucleus, atomic nuclei ...

. In 1965 he began a series of lectures on the physics of quarks that became a "bible for the relatively few who then took it seriously."

Publications

During his lifetime, Dalitz produced numerous publications. One article lists 221 papers, and a total of 26 authored book reviews, public lectures and obituaries, and edited books. Amongst his book reviews was a critical review of

Andrew Pickering Andrew Pickering (born 1948) is a British sociologist, philosopher and historian of science at the University of Exeter. He was a professor of sociology and a director of science and technology studies at the University of Illinois at Urbana-Ch ...

's book ''Constructing Quarks'', in which he takes to task Pickering's implication that experimenters are essentially subservient to theoreticians, saying "In reality, experimenters are cussed individuals, eager to prove the theoreticians wrong whenever possible". His research collaborators included

Hans Bethe Hans Albrecht Eduard Bethe (; ; July 2, 1906 – March 6, 2005) was a German-American physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics and solid-state physics, and received the Nobel Prize in Physi ...

Frank Close Francis Edwin Close (born 24 July 1945) is a particle physicist who is Emeritus Professor of Physics at the University of Oxford and a Fellow of Exeter College, Oxford. Education Close was a pupil at King's School, Peterborough (then a gram ...

F. J. Duarte Francisco Javier "Frank" Duarte (born c. 1954) is a laser physicist and author/editor of several books on tunable lasers. His research on physical optics and laser development has won several awards, including an Engineering Excellence Award in ...

Freeman Dyson Freeman John Dyson (15 December 1923 – 28 February 2020) was a British-American theoretical physics, theoretical physicist and mathematician known for his works in quantum field theory, astrophysics, random matrix, random matrices, math ...

Christopher Llewellyn Smith Sir Christopher Hubert Llewellyn Smith (born 19 November 1942) is an Emeritus Professor of Physics at the University of Oxford. Education Llewellyn Smith was educated at the University of Oxford (BA) and completed his Doctor of Philosophy degr ...

and

Awards and honours

Dalitz was elected a Fellow of the Royal Society (FRS) in 1960 and he received the

Hughes Medal The Hughes Medal is a silver-gilt medal awarded by the Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. T ...

in 1975 "for his distinguished contributions to the theory of the basic particles of matter." He was also awarded the

Maxwell Medal and Prize The Institute of Physics (IOP) awards numerous prizes to acknowledge contributions to physics research, education and applications. It also offers smaller specific subject-group prizes, such as for PhD thesis submissions. Bilateral awards * Th ...

and the Royal Medal. Dalitz was awarded the 1980

J. Robert Oppenheimer Memorial Prize The J. Robert Oppenheimer Memorial Prize and Medal was awarded by the Center for Theoretical Studies, University of Miami, from 1969, until 1984. Established in memory of US physicist J. Robert Oppenheimer, the award consisted of a medal, certifi ...

References

{{DEFAULTSORT:Dalitz, Richard 1925 births 2006 deaths Australian physicists Quantum physicists Particle physicists Theoretical physicists Royal Medal winners Fellows of the Royal Society Maxwell Medal and Prize recipients Academics of the University of Bristol Academics of the University of Birmingham Academics of the University of Oxford Alumni of the University of Cambridge University of Melbourne alumni Australian people of German descent Foreign associates of the National Academy of Sciences Fellows of the American Physical Society