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 caus ...

known for his work in

particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...

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 surve ...

, Victoria, Dalitz studied physics and mathematics at

Melbourne University The University of Melbourne is a public research university located in Melbourne, Australia. Founded in 1853, it is Australia's second oldest university and the oldest in Victoria. Its main campus is located in Parkville, an inner suburb no ...

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

University of Cambridge , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

. His PhD 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 based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron i ...

supervised by

Nicholas Kemmer Nicholas Kemmer (7 December 1911 – 21 October 1998) was a Russian-born nuclear physicist working in Britain, who played an integral and leading edge role in United Kingdom's nuclear programme, and was known as a mentor of Abdus Salam – a N ...

Research and career

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

University of Bristol , mottoeng = earningpromotes one's innate power (from Horace, ''Ode 4.4'') , established = 1595 – Merchant Venturers School1876 – University College, Bristol1909 – received royal charter , type ...

, 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 , mottoeng = Through efforts to heights , established = 1825 – Birmingham School of Medicine and Surgery1836 – Birmingham Royal School of Medicine and Surgery1843 – Queen's College1875 – Mason Science College1898 – Mason Univers ...

. Dalitz moved to

Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to teach an ...

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 s ...

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

University of Oxford , mottoeng = The Lord is my light , established = , endowment = £6.1 billion (including colleges) (2019) , budget = £2.145 billion (2019–20) , chancellor ...

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 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 The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...

. 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 a British-Australian physicist. He introduced the Ward–Takahashi identity, also known as "Ward Identity" (or "Ward's Identities"). Andrei Sakharov said Ward was one of the titans of q ...

, 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 priso ...

. 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 Duarte may refer to: * Duarte (surname), person's surname (or composed surname) and given name * Duarte, California, United States * Duarte Province, Dominican Republic * Pico Duarte Pico Duarte is the highest peak in the Dominican Republic, on th ...

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 nuclei. All commonly o ...

. 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 history of science, 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 Il ...

'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 Bethe (; July 2, 1906 – March 6, 2005) was a German-American theoretical physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics, and solid-state physics, and who won the 1967 Nobel ...

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 gr ...

, F. J. Duarte,

Freeman Dyson Freeman John Dyson (15 December 1923 – 28 February 2020) was an English-American theoretical physicist and mathematician known for his works in quantum field theory, astrophysics, random matrices, mathematical formulation of quantum m ...

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 awarded by the Royal Society of London "in recognition of an original discovery in the physical sciences, particularly electricity and magnetism or their applications". Named after David E. Hughes, the medal is awarded with ...

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 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 * The Max ...

and the Royal Medal. Dalitz was awarded the 1980 J. Robert Oppenheimer Memorial Prize.

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