HomeSciencePhysicsDonald Perkins obituary | Particle physics

Donald Perkins obituary | Particle physics

Particle physicist Donald Perkins, who died at age 97, made groundbreaking discoveries about the structure of the proton and nuclear interactions at extreme energies, and first proposed the use of pion particle beams in cancer therapy. His career spanned the birth of particle physics, as it emerged from studies of cosmic rays in the 1940s, through its maturation in the last decades of the last century, to the climactic discovery of the Higgs particle on the 21st. He played key roles all the time.

When Perkins began research in 1948, the electron, proton, and neutron were the only known fundamental particles whose role in building atoms was understood. The pion, a particle predicted to carry the strong force that binds atomic nuclei, had recently been discovered in cosmic rays by Cecil Powell of the University of Bristol, and it was in Powell’s group that Perkins began his research career.

Powell pioneered the use of photographic emulsions to study cosmic rays. The technique involved going to high altitudes, such as the Pic du Midi, or using specially adapted weather balloons to get the best access to the jets. Perkins’s supervisor was GP Thomson, who had been active in the Second World War, and Perkins asked him to arrange a flight from RAF Benson in Oxfordshire to raise his photographic emulsion 30,000 feet and fly it around for several hours.

Donald Perkins
In addition to research, Donald Perkins lectured extensively and his textbooks continue to educate and inspire new generations of particle physicists.

Over the next few years, Perkins obtained several important images of pawns in action. He was the first to observe the nuclear capture of the negatively charged pion and get proof that the pion is unstable. With Powell and Peter Fowler, Perkins published an encyclopedia of emulsion images of the interactions of cosmic rays, The Study of Elementary Particles by the Photographic Method (1959), which was the state of the art in the field. In 1961, Perkins and Fowler first proposed the use of pion beams as cancer therapy.

Discoveries in cosmic rays inspired the birth of high-energy particle physics using terrestrial accelerators, leading to the discovery of a veritable zoo of particles. That most of these are not fundamental has been suspected, but it was not until 1968 that there was direct evidence that the proton, and implicitly others, are composed of more fundamental particles. The breakthrough came from experiments in Stanford, California, where electrons were used to probe the insides of the proton and neutron. However, the fact that the fundamental components are quarks was not established until 1972 thanks to an insight by Perkins.

One of the avalanches of particle discoveries was that of the neutrino in 1956. This electrically neutral brother of the electron fascinated him. After becoming Professor of Elementary Particle Physics at the University of Oxford in 1965, where he met Denis Wilkinson and Ken Allen, Perkins began using beams of neutrinos, at the Cern laboratory in Geneva, as probes of the proton. There he was directly involved in two groundbreaking discoveries that inspired the modern Standard Model of particles and forces.

Perkins was well aware of the Stanford experiments on electrons and immediately convinced, in 1968, a newly formed collaborative team using Cerns Gargamelle Bubble Room that beams of neutrinos could provide a complementary view of the proton’s internal structure. This idea dominated the neutrino program at Cern, and by 1972 their data made it possible to measure the electrical charge of those constituents. The result: the proton and neutron are made up of quarks bound together by gluons. By 1973, this had inspired the development of the modern quantum chromodynamics theory of the strongly interacting particles, an important foundation of the Standard Model.

The strong nuclear force was understood, but the weak force, whose most well-known role is to power the sun and cause forms of radioactivity, remained a mystery. A new theory, which unites the weak force with the electromagnetic force, has now received its first confirmation thanks to Perkins and the Gargamelle group. Neutrinos are a unique probe of the weak force. They were known to pick up electrical charge when interacting with protons, but the emerging theory unifying electromagnetic and weak interactions required the existence of a previously unseen consequence of the weak force by which neutrinos bounce unchanged against protons.

Donald Perkins, right, and Norman Barford sink a pipe into the Aletsch Glacier on the Jungfraujoch in the Bernese Alps in 1948 to test whether ice can be used to detect particles
Donald Perkins, right, and Norman Barford sink a pipe into the Aletsch Glacier on the Jungfraujoch in the Bernese Alps in 1948 to test whether ice can be used to detect particles

The Gargamelle experiment played a leading role in establishing the existence of these “neutral currents”, which paved the way for the eventual confirmation of the unified theory and the 1979 Nobel Prizes for the theoretical originators, Sheldon Glashow, Abdus Salam and Stephen Weinberg. At the time of their attribution, the agents of unification, the massive W and Z bosons, had not yet been discovered. The Gargamelle results, largely driven by Perkins, were considered sufficient evidence by the Nobel Committee.

Perkins was a member of Cern’s science policy committee from 1981 to 1986 and later chair, a period when LEP, the Large Electron-Positron Collider and predecessor of the current one Large Hadron Collider was built. With the standard model established, the long march to find its foothold, the Higgs boson, began. Perkins’ graduate handbook, Introduction to High Energy Physics, first published in 1972, is now in its fourth edition and continues to educate and inspire new generations of particle physicists working at the Large Hadron Collider.

Born in Hull, East Yorkshire, Donald was the son of Gertrude and George Perkins, teachers of English and Mathematics. After his education at the town’s Malet Lambert Secondary School, he attended Imperial College London, where he received a BSc in Physics in 1945 and a PhD in 1948. Royal Commission for the Exhibition of 1851 three years, before becoming a physics assistant at the University of Bristol in 1951. After a year at the Lawrence radiation laboratory, at Berkeley in California, he returned to Bristol in 1956 as a lecturer in physics, appointed reader in 1960. He was at Oxford University, where from 1965 he was a fellow of St Catherine’s College. until his retirement in 1993.

After being elected a Fellow of the Royal Society in 1966, he won the Society’s Royal Medal in 1997. In 1991 he was appointed CBE.

Perkins married Dorothy Maloney in 1955. She died in 2021, and he is survived by their two daughters, Venetia and Michele.

Donald Hill Perkins, particle physicist, born October 15, 1925; died October 30, 2022

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