Particle physicist Donald Perkins, who died at the age of 97, made fundamental discoveries about proton structure and nuclear interactions at extreme energies, and was the first to propose the use of particle beams from pawns in the treatment of cancer. His career spanned from the birth of particle physics, as it emerged from studies of cosmic rays in the 1940s, through its maturation in the closing decades of the last century, to the breakthrough discovery of the Higgs boson at the 21st. He played key roles throughout.
When Perkins began his 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 believed 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 career as a searcher.
Powell had pioneered the use of photographic emulsions to study cosmic rays. The technique consisted of going to high altitude, such as the Pic du Midi, or using suitable weather balloons, to best access the rays. Perkins’ 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 take his photographic emulsion up to 30,000 feet and fly it for several hours.
Over the next few years, Perkins obtained several significant images of pawns in action. He was the first to observe the nuclear capture of the negatively charged pion and obtained proof that the pion is unstable. Along with Powell and Peter Fowler, Perkins published an encyclopedia of emulsion images of cosmic ray interactions, 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 suggested the use of pion beams as a treatment for cancer.
Discoveries in cosmic rays inspired the birth of high-energy particle physics using terrestrial accelerators, which led to the discovery of a real particle zoo. It was suspected that most of them are not fundamental, but it was not until 1968 that there was direct evidence that the proton, and by implication others, are composed of more fundamental particles. The breakthrough had come from experiments at Stanford, California, where electrons were used to probe inside the proton and neutron. That the fundamental constituents are quarks, however, was not established until 1972, thanks to an idea by Perkins.
Among the avalanche of particle discoveries, there was that of the neutrino, in 1956. This electrically neutral brother of the electron fascinated him. After becoming a professor of elementary particle physics at the University of Oxford in 1965, where he built the modern nuclear physics department with Denys Wilkinson and Ken Allen, Perkins began using neutrino beams at the CERN laboratory. in Geneva, as proton probes. There he was directly involved in two groundbreaking discoveries that inspired the modern standard model of particles and forces.
Perkins was well informed of Stanford’s experiments with electrons and immediately, in 1968, convinced a newly formed collaborative team using CERN’s Gargamelle bubble chamber that neutrino beams could provide a complementary view of the internal structure of the proton. This idea dominated CERN’s neutrino program and, in 1972, their data made it possible to measure the electrical charges of these constituents. Result: the proton and the neutron are made up of quarks, bound together by gluons. By 1973, this had inspired the development of the modern theory of quantum chromodynamics of strongly interacting particles, a key foundation of the Standard Model.
The strong nuclear force was understood, but the weak force, whose most familiar role is to power the sun and cause forms of radioactivity, remained an enigma. A new theory, uniting 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 an electric charge when they interact with protons, but the emerging theory uniting electromagnetic and weak interactions demanded the existence of a novel consequence of the weak force in which neutrinos bounce off protons unchanged.
The Gargamelle experiment played a leading role in establishing the existence of these “neutral currents”, which paved the way for eventual confirmation of the Unified Theory and Nobel Prizes in 1979 to its theoretical creators, Sheldon Glashow, Abdus Salam and Steven Weinberg. At the time of their assignment, the unifying agents, the massive W and Z bosons, had not yet been discovered. Gargamelle’s results, largely inspired by Perkins, were judged as sufficient evidence by the Nobel committee.
Perkins was a member of CERN’s Science Policy Committee from 1981 to 1986, and later its chairman, a period when LEP, the Large Electron-Positron Collider and precursor to the current Large Hadron Collider was under construction. Once the standard model was established, the long march to find its fulcrum, the Higgs boson, began. Perkins’ graduate textbook, 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 in Large Hadron. Collide.
Born in Hull, East Yorkshire, Donald was the son of Gertrude and George Perkins, English and Maths teachers respectively. Educated at Malet Lambert High School in the city, he went on to Imperial College London, where he obtained a BSc in physics in 1945 and his doctorate in 1948. He was a senior researcher for the Royal Commission for the Exposure of 1851 for three years, before becoming an Associate in Physics in 1951 at the University of Bristol. After a year at the Lawrence Radiation Laboratory in Berkeley, California, he returned to Bristol in 1956 as a lecturer in physics, appointed reader in 1960. He was at the University of Oxford, where he received a scholarship from St Catherine’s College, from 1965 until his retirement in 1993.
Having been elected a Fellow of the Royal Society in 1966, he was awarded the Society’s Royal Medal in 1997. He was appointed CBE in 1991.
Perkins married Dorothy Maloney in 1955. She died in 2021 and he is survived by their two daughters, Venetia and Michele.
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