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Cormac O'Ceallaigh (29 July 1912 in Dublin – 10 October 1996 in Dublin) was an Irish physicist who worked in the fields of cosmic ray research and elementary particle physics.

His father was a prominent Dublin obstetrician. He married 1939 Millie Carr in 1939; they had three daughters.

When speaking at conferences, he was known for his sparkling wit.

Early life and education

O'Ceallaigh entered University College, Dublin (UCD) to study physics in 1930 and completed his undergraduate work in 1934. He got a post graduate scholarship and worked for one year in Paris with the eminent cosmic ray physicist Pierre Auger. From 1935 to 1938 he did postgraduate research at the Cavendish Laboratory, Cambridge, where he was mentored by Lord Rutherford and concentrated on nuclear physics. He obtained a lectureship at University College Cork in 1937 and returned to Ireland in 1938. He remained at Cork until 1947 and then took a position at the University of Bristol.

At Bristol he worked in a group assembled by the Nobel Prize winning particle physicist C F Powell. Bristol was at the time the worldwide center of cosmic ray research, and O'Ceallaigh, nurtured by Rutherford and Powell, two of the greatest experimental physicists in history, soon became one of its leading figures. Their research into cosmic rays, involving pions, kaons, and even neutrinos, helped to establish the The Standard Model of particle physics.

From 1953 to 1984 O'Ceallaigh was Senior Professor and Head of the Cosmic Ray Section at the Dublin Institute for Advanced Studies (DIAS).

all about the medal

Professor O'Ceallaigh’s most important work involved the strange new particles in cosmic ray interaction events which were just beginning to be discovered at the time, in particular the K mesons.

Awards and honours

In 1951, O'Ceallaigh was elected Fellow of the Royal Irish Academy. He was also a Council Member of the European Physical Society. He gained an 1951 Commonwealth Fellowship.

He was awarded the Boyle Medal in 1979.

In 1999 DIAS and the estate of Cormac O'Ceallaigh jointly established a medal in his name. The medal recognizes scientists who have made important contributions to Cosmic Ray Physics and is presented at the opening ceremony of the biennial International Cosmic Ray Conference.

Papers

• “Masses and modes of decay of heavy mesons.—Part I. κ-particles” The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, Series 7, Volume 42, 1951
• "Observations on the multiple scattering of ionizing particles in photographic emulsions.—Part II. The scattering of positrons at 105 and 185 MeV" [with M.G.K. Menon & O. Rochat] The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, Series 7, Volume 42, 1951

External links

• O’Ceallaigh Medal recipients

Category:Alumni of University College Dublin Category:Alumni of the University of Cambridge Category:Academics of University College Cork Category:Academics of the University of Bristol‎ Category:Academics of the Dublin Institute for Advanced Studies Category:Irish physicists Category:20th-century physicists Category:Cosmic ray physicists Category:Scientists of the Cavendish Laboratory Category:1912 births Category:1996 deaths

Obit from the Irish Times

Professor Cormac O Ceallaigh, one of the most distinguished Irish scientists of this century, died on October 10th in Dublin, at the age of 84. He was the son of an eminent Dublin obstetrician. In 1930, he entered UCD to study physics. Obtaining a post graduate scholarship in 1934, he went to Paris, working in the laboratory of Pierre Auger. Three years in Cambridge followed, and he returned to Ireland in 1938. He had been appointed to a lectureship in Cork in 1937.

During the war years he managed to continue research in Cork, and published work, but in 1949 he applied for leave of absence to work abroad. He visited former colleagues from Cambridge in Oxford and Harwell, but was unable to obtain a suitable position. Finally he arrived in Bristol and was offered a modest post by Professor C. F. Powell. It was a fortunate outcome, for Powell had gathered a colourful and talented group from all over the world; and it seems fair to say that Bristol at that time was the best physics university in the world. Cormac and his wife Millie made a considerable financial sacrifice to go there.

Powell had introduced a technique which had languished in obscurity. It was called the nuclear emulsion method, and basically consisted of thick photographic films stacked together and exposed to cosmic ray particles. The tracks made in the emulsions could be followed and measured by scanners and physicists, using microscopes. It was enormously effective.

It was a golden age in physics. Most European physicists had been working on radar during the war and returned eagerly to their laboratories to take up work unfinished since 1939. There was, therefore, a great upsurge in basic physics between 1945 and 1950. New, strange, unstable particles were discovered. To gain access to the cosmic rays which produced unstable particles, physicists took their equipment up mountains or flew enormous balloons to great heights, a dangerous undertaking.

Cormac rapidly became a leading figure in Bristol. Given his ebullient temperament, one might have thought that his physics would perhaps be brilliant but erratic. It was brilliant, but not erratic; it was careful and painstaking. In his work on one particular reason, the Kappa, he examined over 700 particle decays in emulsion to find just two of the Kappa mesons.

In 1953 he was appointed a senior professor in the School of Cosmic Physics in the Dublin Institute for Advanced Studies. He held this post for 29 years, until his retirement in 1982. He built up an emulsion group, which joined a large international collaboration. Later he took his group into a project which used accelerators instead of cosmic rays. After some years, though, he returned to cosmic rays. This time he used a new material, a plastic sheet which responds to very highly charged primary particles. Large areas of this were carried on a satellite, to expose them to the primaries. This work continues successfully in the institute.

At conferences, he was a brilliantly witty speaker. Apart from his physics and his family, he had two great activities. One was cabinet making, at which he was highly skilled; the other was sailing. In his yacht club he was known as "The Voice", because in full flight he could be heard all over the coal harbour in Dun Laoghaire.

His wife Millie died in 1987. We offer our sympathy to his daughters, his grandchildren and great granddaughter, and remember him with gratitude.

Obit from The Independent

Emeritus Professor of Physics at the Dublin Institute for Advanced Studies, was one of the most distinguished physicists in Ireland. His research field was that of cosmic rays and elementary particle physics, to which subjects he made many seminal contributions.

The son of a prominent Dublin obstetrician, O Ceallaigh's career as a scientist started at University College, Dublin. His postgraduate research was carried out at the Cavendish Laboratory, Cambridge from 1935 to 1938, after a year in Paris with the great French cosmic ray physicist, Pierre Auger. At Cambridge, O Ceallaigh worked in the field of nuclear physics, coming directly under the eye and the influence of Lord Rutherford. A brilliant scholar, he gained an 1851 (Commonwealth) Fellowship, the award being announced to him by Rutherford in a chance encounter with the admonition "I see that you've wangled it again, O'Kelly!"

After some years as a lecturer at the University of Cork, O Ceallaigh joined C.F. Powell's group at Bristol, from 1949 to 1952. This was something of a golden era for physics in Britain, when revolutionary new discoveries in cosmic rays occurred almost daily. Of several important experiments undertaken by O Ceallaigh, one regarding the nature of the neutral particle (neutrino) emitted in the decay of an elementary particle called the pion, stands out and has ramifications to this day. The exact nature of this neutrino remains a puzzle: it impacts on the observed deficit of neutrinos from the sun, and on how very massive stars, in their final death throes, explode as supernovae.

In 1953, O Ceallaigh took up the post of Senior Professor in Cosmic Ray Physics at the Dublin Institute for Advanced Studies. There he continued his association with Bristol University, concentrating on the study of the superheavy nuclei in the cosmic rays (those heavier than iron and nickel), using special plastic detectors carried in the stratosphere by unmanned balloons in very long flights (sometimes even crossing the Atlantic).

These experiments continued through the 1960s and early 1970s, to be followed by even more ambitious ventures. Huge detector arrays, 10 square metres or more in area, were prepared by O Ceallaigh and his colleagues in Dublin, to be carried and launched into earth orbit on flights of the US Space Shuttle. Intended for a one-year exposure, due to various failures the equipment was to stay in orbit for six years before being recovered. This had the fortunate consequence that it provided by far the most prolific data available on the fluxes of the very heaviest nuclei.

In particular, these included nuclei heavier than bismuth (those in the actinide series, such as uranium, plutonium and californium). We believe that these are produced as a result of very rapid neutron capture processes which occur, and only occur, in the course of supernova explosions.

In a sense therefore, O'Ceallaigh's work came full circle: 99 per cent of the prodigious energy released in a supernova outburst is in the form of invisible neutrinos, and although not yet fully understood, our computer models of the explosive mechanism - whether it blossoms or stalls - seem to depend critically on the nature of those neutrinos and their interactions: indeed, precisely those questions that O Ceallaigh had been addressing in a quite different context 40 years previously.