Richard Dalitz

Richard Henry Dalitz
Born	28 February 1925 Dimboola, Australia
Died	13 January 2006 Oxford, England
Nationality	Australian, British
Fields	Physics
Institutions	University of Bristol University of Birmingham Cornell University Enrico Fermi Institute University of Oxford
Alma mater	Melbourne University Cambridge University
Doctoral advisor	Nicholas Kemmer
Doctoral students	Frank Close Christopher Llewellyn Smith Stanley Mandelstam
Known for	Dalitz plot Dalitz pair CDD poles
Notable awards	Maxwell Medal and Prize (1966) Hughes Medal (1975) Royal Medal (1982) Harrie Massey Medal and Prize (1990)

Richard Henry Dalitz, FRS (28 February 1925 – 13 January 2006) was an Australian physicist known for his work in particle physics.^[1][2]

Born in the town of Dimboola, Victoria, Dalitz studied physics and mathematics at Melbourne University before moving to the United Kingdom in 1946, starting his PhD research at the University of Cambridge. After two years 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,^[3] although keeping a connection with Chicago until 1966. He retired in 1990.

Physics

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.^[1] The Dalitz plots were discovered in 1953, while he was at Cornell.

Dalitz plots^[4][5] play a central role in the discovery of new particles in current high-energy physics experiments, including Higgs boson research,^[1] and are tools in exploratory efforts that might open avenues beyond the standard model.^[6]

Furthermore, Dalitz was directly involved in pioneering quark research and he participated in the identification of the top quark.^[2] His various fundamental contributions have led to practitioners in the field to identify Dalitz as one of particle physics "greatest unsung scientists."^[1]

Quantum mechanics

Dalitz was an old and close friend of John Clive Ward, the creator of the Ward Identities.^[7] Their friendship began around 1948 when Dalitz independently derived Ward's results^[8] for the polarisation entanglement of two photons propagating in opposite directions.^[9] Dalitz was the lead author of a succinct, and yet revealing, account of Ward's physics.^[10] While commenting on the physics sorrounding 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."^[10]

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.^[2] 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".^[11]

Recognition

Dalitz was made a Fellow of the Royal Society in 1960 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.^[12][13]

Dalitz's friends and co-authors (partial list)

• Hans Bethe
• Frank Close
• F. J. Duarte
• Freeman Dyson
• Nicholas Kemmer
• Rudolf Peierls
• Christopher Llewellyn Smith
• John Clive Ward

References

1. Close, Frank (24 January 2006). "Richard Dalitz: Physicist who mapped the behaviour of exotic particles and argued for the reality of quarks". The Guardian.
2. Ian J.R. Aitchison; Frank E. Close; Avraham Gal; & D. John Millener (2 February 2008). "The scientific heritage of Richard Henry Dalitz". arXiv:physics/0603219.
3. Close, Frank (July 2006). "Obituary: Richard Henry Dalitz". Physics Today 59 (7): 65–66. Bibcode:2006PhT....59g..65C. doi:10.1063/1.2337841.
4. 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.
5. 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.
6. P. Pakhlov and T. Uglov, Flavor physics at Super B-factories era, J. Phys.: Conf. Ser. 675, 022009 (2016).
7. F. J. Duarte, The man behind an identity in quantum electrodynamics, Australian Physics 46 (6), 171–175 (2009)
8. M. H. L. Pryce and J. C. Ward, Angular correlation effects with annihilation radiation, Nature 160, 146 (1947).
9. J. C. Ward, Memoirs of a Theoretical Physicist (Optics Journal, New York, 2004).
10. R. H. Dalitz and F. J. Duarte, John Clive Ward, Physics Today 53 (10), 99–100 (2000).
11. "Fundamental Developments: (review of) Constructing Quarks: A Sociological History of Particle Physics by A. Pickering", Nature 314 (6009), 28 March 1985: 387–388, Bibcode:1985Natur.314..387D, doi:10.1038/314387a0
12. Walter, Claire (1982). Winners, the blue ribbon encyclopedia of awards. Facts on File Inc. p. 438. ISBN 9780871963864.
13. "Dalitz receives Oppenheimer Prize". Physics Today (American Institute of Physics): 67. April 1980. doi:10.1063/1.2914032. Retrieved 1 March 2015.

External links

• Richard Dalitz at The Guardian
• Richard Dalitz at Nature