It is with great sadness that the Department of Physics shares the news of the death of John Cobb. Emeritus Professor Wade Allison writes:
John Henry Cobb, born 15 May 1949, died on 29 July 2024 after a short Illness. He is survived by Sue Morton, his partner of 40 years. Together they enjoyed travel and active holidays around the world.
John was born in Harrow and educated at Harrow County School for Boys. In 1968 he came to Oxford as a physics scholar at Keble where he gained a First Class in both Mods and Finals. In 1971, at Wolfson, he began work for his DPhil thesis, ‘Some electromagnetic interactions of high velocity particles with matter’, that included significant new work on transition radiation, energy loss and the drift and diffusion of electrons in gases. In 1975 he was awarded his doctorate. Subsequently in posts at Brookhaven, Lancaster and then back at Oxford, he put the experience and understanding developed in his thesis to work, making crucial contributions to the design of several experiments that have transformed our knowledge of particle physics. As a Senior College Lecturer at Keble for 40 years, he enjoyed giving physics tutorials until shortly before his death.
Notably, his work on the theory and experimental evidence for X-ray transition radiation, was crucial to the identification of electrons emitted from the decay of the J/Psi resonance at the CERN Intersecting Storage Rings (ISR) in a pioneering experiment that he joined in 1975. This put transition radiation on the map as a reliable method of flagging ultra-relativistic charged particles.
Another experiment in which John played a decisive role was the UK/US Soudan2 search for proton decay. This called for the continuous fine-grained observation of a 1,000 tonne mass deep in a disused mine in Minnesota for over a decade. John’s revolutionary design worked well, and although the experiment found no evidence for proton decay, the observed background of neutrinos passing right through the Earth showed evidence for flavour oscillations. This provided important support for other experiments based on Cherenkov signals in water. The revolutionary result was investigated further in the Main Injector Neutrino Oscillation Search (MINOS) experiment with its 720 km baseline. Here too, John’s contribution was to the design and its successful operation.
In the new millennium, John joined the Muon Ionisation Cooling Experiment (MICE) designed to prove the feasibility of muon cooling for a possible muon collider. His work on the superconducting magnets contributed to its success, as published in Nature.
Throughout these and other experiments John earned deep respect and confidence among all who worked with him, in particular his graduate students, many of whom went on to distinguished careers. His technical integrity was always beyond question. He inspired the lives of many and added to the field of experimental physics. He will be missed by all who were lucky enough to work with him in the USA, Rutherford Laboratory and Oxford.
A service of thanksgiving will take place on 20 August at 11.30am at St Nicholas Church, Fyfield. Donations in lieu to Sobell House may be made on the day or may be sent c/o Peter Smith & Son Funeral Directors Ltd, 135 Burwell Drive, Witney, Oxon, OX28 5LP.