# Richard Dalitz

Richard Henry Dalitz, FRS[1] (28 February 1925 – 13 January 2006) was an Australian physicist known for his work in particle physics.[3][4]

Dick Dalitz
Born Richard Henry Dalitz
28 February 1925
Dimboola, Australia
Died 13 January 2006 (aged 80)
Oxford, England
Nationality Australian, British
Alma mater Melbourne University
University of Cambridge
Known for Dalitz plot
Dalitz pair
CDD poles
Awards
Scientific career
Fields Particle physics
Quantum mechanics
Institutions University of Bristol
University of Birmingham
Cornell University
Enrico Fermi Institute
University of Oxford
Thesis Zero-zero transitions in nuclei (1950)
Doctoral students Frank Close[citation needed]
Christopher Llewellyn Smith[citation needed]
Stanley Mandelstam[citation needed]
Crispin Gardiner

## Education and early lifeEdit

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[5] supervised by Nicholas Kemmer.[2]

## Research and careerEdit

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,[6] although keeping a connection with Chicago until 1966. He retired in 1990.[7]

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.[3] The Dalitz plots were discovered in 1953, while he was at Cornell.

Dalitz plots[8][9] play a central role in the discovery of new particles in current high-energy physics experiments, including Higgs boson research,[3] and are tools in exploratory efforts that might open avenues beyond the standard model.[10]

His various fundamental contributions have led to practitioners in the field to identify Dalitz as one of particle physics "greatest unsung scientists"[3] and "a theorist exceptionally valued by experimentalists."[1]

### Quantum mechanicsEdit

Dalitz was an old and close friend of John Clive Ward, the creator of the Ward Identities.[11] Their friendship began around 1948 when Dalitz independently derived Ward's results[12] for the polarisation entanglement of two photons propagating in opposite directions.[13] Dalitz was the lead author of a succinct, and yet revealing, account of Ward's physics.[14] While commenting on the physics surrounding the derivation of the probability amplitude

${\displaystyle \left|\psi \right\rangle =(\left|x,y\right\rangle -\left|y,x\right\rangle )}$

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."[14]

### QuarksEdit

Dalitz was directly involved in pioneering quark research since the early 1960s,[1] at a time when leading theorists considered quarks as purely mathematical entities,[15] and he participated in the identification of the top quark.[4] 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."[1]

### PublicationsEdit

During his lifetime, Dalitz produced numerous publications. One article[16] lists 221 papers, and a total of 26 authored book reviews, public lectures and obituaries, and edited books.[4] Amongst his book reviews was a critical review of Andrew Pickering'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,[citation needed] Frank Close,[citation needed] F. J. Duarte,[citation needed] Freeman Dyson,[citation needed] Nicholas Kemmer,[2] Rudolf Peierls,[citation needed] Christopher Llewellyn Smith[1] and John Clive Ward.[14]

## Awards and honoursEdit

Dalitz was elected a Fellow of the Royal Society (FRS) in 1960[1] and he received the Hughes Medal in 1975 "for his distinguished contributions to the theory of the basic particles of matter." He was also awarded the Maxwell Medal and Prize and the Royal Medal. Dalitz was awarded the 1980 J. Robert Oppenheimer Memorial Prize.[17][18]

## ReferencesEdit

1. Aitchison, Ian J. R.; Smith, Christopher Llewellyn (2016). "Richard Henry Dalitz. 28 February 1925 — 13 January 2006". Biographical Memoirs of Fellows of the Royal Society. London: Royal Society. 62: 59–88. doi:10.1098/rsbm.2016.0019.
2. ^ a b c
3. ^ a b c d Close, Frank (24 January 2006). "Richard Dalitz: Physicist who mapped the behaviour of exotic particles and argued for the reality of quarks". The Guardian.
4. ^ a b c Ian J.R. Aitchison; Frank E. Close; Avraham Gal; & D. John Millener (2 February 2008). "The scientific heritage of Richard Henry Dalitz". Nuclear Physics A. 771: 2–7. arXiv:physics/0603219. Bibcode:2006NuPhA.771....2C. doi:10.1016/j.nuclphysa.2006.03.007.
5. ^ Dalitz, Richard Henry (1950). Zero-zero transitions in nuclei (PhD thesis). University of Cambridge.
6. ^ Close, Frank (July 2006). "Obituary: Richard Henry Dalitz". Physics Today. 59 (7): 65–66. Bibcode:2006PhT....59g..65C. doi:10.1063/1.2337841.
7. ^ Ross, Graham (2006). "Obituary: Richard Dalitz (1925–2006)". Nature. 440 (7081): 162–162. Bibcode:2006Natur.440..162R. doi:10.1038/440162a. PMID 16525459.
8. ^ R. H. Dalitz (1953). "On the analysis of τ-meson data and the nature of the τ-meson". Philosophical Magazine. 44: 1068. doi:10.1080/14786441008520365.
9. ^ R. H. Dalitz (1954). "Decay of τ mesons of known charge". Physical Review. 95 (4): 1046. Bibcode:1954PhRv...94.1046D. doi:10.1103/PhysRev.94.1046.
10. ^ P. Pakhlov and T. Uglov, Flavor physics at Super B-factories era, J. Phys.: Conf. Ser. 675, 022009 (2016).
11. ^
12. ^ Pryce, M. H. L.; Ward, J. C. (1947). "Angular Correlation Effects with Annihilation Radiation". Nature. 160 (4065): 435–435. Bibcode:1947Natur.160..435P. doi:10.1038/160435a0.
13. ^ J. C. Ward, Memoirs of a Theoretical Physicist (Optics Journal, New York, 2004).
14. ^ a b c Dalitz, Richard H.; Duarte, Frank J. (2000). "John Clive Ward". Physics Today. 53 (10): 99–100. Bibcode:2000PhT....53j..99D. doi:10.1063/1.1325207.
15. ^ F. Close, The Infinity Puzzle (Oxford University Press, Oxford, 2011).
16. ^ "Fundamental Developments: (review of) Constructing Quarks: A Sociological History of Particle Physics by A. Pickering", Nature, 314 (6009): 387–388, 28 March 1985, Bibcode:1985Natur.314..387D, doi:10.1038/314387a0
17. ^ Walter, Claire (1982). Winners, the blue ribbon encyclopedia of awards. Facts on File Inc. p. 438. ISBN 9780871963864.
18. ^ "Dalitz receives Oppenheimer Prize". Physics Today. American Institute of Physics. 33: 67. April 1980. doi:10.1063/1.2914032. Retrieved 1 March 2015.