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Home , Carlo Rubbia

Phys. Buii., Vol. 36, 1985. Printed in Great Brnam

Portsmouth. At both mburaturics hc worked under Professor Harrie Massey, first on countcrmcasurcs to magnctnc mim2s.lz1tcr on thc design and development of a series of British noncontact mines. Apart from operational research aspects. this work involved a considerable amount of classical, applied mathematics. During this time he was elected to a Research Fel lowship at St John`s. ln l945 John Gunn took up a lectureship in applied mathematics at Manchester with Professor S Goldstein, and also undertook research on two topics in fluid mechanics ·— The 1984 Nobel Iaureates in physics are relaxation phenomena in shock waves, and Carlo Rubbia and linearised supersonic aerofoil theory. ln of CERN, for their contributions to the 1946 he moved to London as a lecturer in discovery ofthe W and Z particles Professor Massey’s department (applied mathematics at that time) at University Col lege to further his research interest in the ‘quantum mechanical’ subjects of nuclear and . While there he worked on the scattering of vector mesons in a Douglas R O Morrison potential field. Then, in 1949, he was appointed to the Cargill Chair of Natural Philosophy at Glasgow University, which he held for 33 years until his retirement in 19s2. In his early days at Glasgow John Gunn The 1984 in physics is excep the role that individuals play in it. had the task of building up the theoretical tional. Firstly in that, because the experi The project is an exceptional one that side of the department which was being ment was so important and clear, the prize would have sounded like science fiction 20 developed under the leadership of P 1 Dee was awarded only one year after the results years ago - to produce ; to store as a centre of nuclear physics activity. His had been obtained instead of waiting some it; to accelerate it to such high energies that own research was in nuclear structure and in years for confirmation. Secondly, for the particles a hundred times as heavy as the meson photo-production. After 1957 he first time the prize was given not just to are produced, which can then be took an increasing interest in the develop individuals but also to a large project. Both detected against a background of l0lother ing national and intemational programme laureates, Carlo Rubbia and Simon van der interactions. In addition, these new par of high energy physics, being involved in the Meer, say they feel that the prize is awarded ticles (W and Z) are the observable proof of early planning of the electron synchrotron also to their colleagues and indeed to a theory that unifies two of the four funda MNA round which the Daresbury Laborat CERN, the European Laboratory for Par mental forces of nature. ory was built. He joined the newly formed ticle Physics where the project was carried Nuclear Physics Board of the SRC in 1965 out. and was a member of the CERN Council for The actual wording of the Nobel citation two years. is ‘for their decisive contributions to the It was Einstein‘s dream to unify all the for From 1968 to 1972 he was a member of large project which led to the discovery of ces of nature - to have one theorv that the SRC, becoming Chairman of the Nuc the field particles W and Z, communicators would allow the forces to appear differently lear Physics Board in 1970. He then became of weak interactions’. ln some ways it re in our present energy range. Two of the a member of the University Grants Com cognises what is called ‘Big Science’ and forces are familiar - and electro mittee, until 19Sl, for the most part as magnetism (Clerk Maxwell could be con Chairman of the Physical Services and sidered the first unifier of electrical and * Equipment Subcommittees. Sir John was magnetic forces). The weak force controls instrumental in the proposal for ‘New Carlo Hubbia the relatively slow decay of radioactive par blood` appointments and in its later ticles, whilst the strong force holds the pro development, and also in instigating the tons and neutrons together in the nucleus increase of university grants to something despite the electromagnetic repulsion. approaching their correct level. In addition , and Shel to these duties, he was Head of the Natural don Glashow produced a theory (for which Philosophy Department in Glasgow they were awarded the Nobel prize in 1979) (1972-82) and Vice—Principal of the Uni combining the electromagnetic and weak versity (1971-5). forces to give a single force - the electro John Gunn was made a Commander of weak. The essential point of this theory is the British Empire in 1976 and Knight that two particles interact by exchanging a Bachelor in 1982. He holds Honorary DScs virtual particle or quantum. lf charge is from both Heriot-Watt and Loughborough exchanged then the virtual particle is the universities. ln retirement he still under Vlfe`, but if no charge is exchanged then the takes various tasks for the SERC I virtual particle is the Z° or a . The photon is massless but the W and Z" masses were calculated to be ~82 and 94 GeV respectively. Thus the Z° is sometimes called ‘heavy light', as it is a mas t ri l j‘}'!'j sive photon. The theory predicted weak neutral currents (Z" exchange) and these were first observed at CERN in 1973. it 5 t ei ti . However. the most dramatic confirmation of the theory would have been the direct i)2i3%t J? ·· iq fig r dei L? is observation of the W and Z as real particles.

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The immense contribution of Carlo Rubbiu chamber-like manner. Outside this were was to scc how this could bc done. and then electromagnetic and hadron calorimeters, to inspire thc cntirc project in mastcrly fush detectors and a magnet, the whole ion. weighing some 2000 tons. Another team led by constructed a slightly simpler detector, the UA2 (UA stands for underground area). Aftcr preliminary unsuccessful discussions The first runs in 1981 had too low an with Fcrmilab, Carlo Rubbia proposed to Q `` intensity for a reasonable chance of seeing CERN in 1976 that bc pro 5 -Q . A " W and Z production, but the increased i``i` duced from the PS accelerator, stored until it ~ intensity in 1982 allowed the UA1 and enough were accumulated and then UA2 groups to demonstrate W production injected into the large (6.8 km circumfer i ri ·iiii~r<‘§lis; in January 1983 and UA1 to report Z" pro we ence) SPS accelerator where they would . il "‘”`€¢?%i*‘?‘i€¥ duction in June 1983 (the results are then collide with circulating in the is is ’ . · N ss t. -- / described in more detail in an article by opposite direction. With 270 GeV in each published in the October beam, thc pp annihilation would give 1983 issue of Physics Bulletin). 540 GeV in the centre of mass — enough to produce the W and Z°. CERN already had experience of colliding beam machines, having built the first one for hadrons, the ' lfilflf Carlo Rubbia was born in 1934 in , lntersecting Storage Rings (ISR), where two c“*°* ltaly and studied at the Scuola Normale in separate beams of protons each with an E- lift}: I irxii. , and then at Pisa, Columbia and Rome energy of 31 GeV collided with a force Simon vari der Meer universities before joining CERN in 1960. equivalent to a 2000 GeV proton hitting a Since 1972 he has been a professor at Har stationary target. An exceptional thing vard. Simon van der Meer was born in 1925 about the pp proposal was that since the at The Hague in The Netherlands. After particles had opposite sign and equal mass, studying at Delft he joined Philips before both beams could be accelerated in the phase space is then distorted by the correc coming to CERN in I956. same vacuum ring at the same time. The tion applied so that the particles move in The two laureates are of very different idea was not completely new: in i966 Bud towards the centre while the empty space character. Carlo Rubbia is exuberant and ker and Skrinsky atNovosibirsk had sugges moves outwards — thus the total volume of hard-driving, and with success has moved to ted that this might be possible. The great phase space is constant. a higher plane. Simon van der Meer is rela advantage of CERN was the strength and was tried in 1974 with tively quiet and hopes to continue to work excellence of its accelerator staff who had the ISR and proved to work. but the effi as before, though he realises that he may built several machines to exacting stan ciency was low as the proton beams were so have more public duties. There are many dards, and this was a major reason for the intense. anecdotes about Carlo, but Simon’s col success of the CERN project. Carlo Rubbia’s proposal was strongly leagues do not remember any special story. supported by the CERN Directors General, The day the Nobel prize was announced was Leon van Hove and Sir John Adams. A perhaps not untypical. Carlo was in a taxi small experimental ring (Initial Cooling going to an airport when a flash on the radio There was, however, a major problem Experiment, ICE) was used to test both elec announced the prize. At first, the taxi how to collect enough antiprotons. When tron and stochastic cooling. The stochastic driver did not believe that his passenger was the protons hit their target the antiprotons cooling, modified by the Thorndahl the laureate, but then offered him a free are produced with a wide spread in momen method, was found to be nearly good ride. Simon was working quietly in his office tum and angle - but only a few with the enough. So, after extensive studies, it was when he received the telephone call. A correct momentum and angle range can be decided to proceed with the project in July horde of reporters descended on CERN. accepted and trapped in a storage ring cal 1978. Simon van der Meer had a major That day Simon gave some 50 individual led an accumulator. The basic share in the planning and construction of interviews before asking to be excused. It problem is Liouville’s theorem which says the which was would be a mistake to believe they are com that the total phase Space volume ofthe completed by July 1980. The rapid progres pletely opposite in character, however,. beam is constant (it is sometimes likened to sion of the entire project was stimulated by since both are very intelligent, very hard squeezing a closed toothpaste tube — the Carlo Rubbia’s interest and drive. working and completely devoted to the pro shape may change but the cross sectional ject they are working on. area stays the same). ln 1966 Budkcr sug In conclusion, the 1984 Nobel prize was gested a solution — to ‘coo1’ (i.e. reduce the awarded to two brilliant individuals, each of spread in momentum and angle of) the Another major problem was to design and whom played a crucial part in a very large beam by injecting an intense beam of elec construct a detector which could distinguish project. Both emphasise that they consider trons which would travel with the same vel a W or a Z. decay against a background the prize also recognises the excellent work ocity as the protons. In 1968, Simon van der of 10* interactions. Carlo Rubbia had a done by large teams of people. It could be Meer suggested and did detailed calcula tremendous reputation of being a wizard at considered as the final coming of age of tions on another solution called ‘stochastic building detectors and getting them work CERN, a consequence of the many years of cooling'. The basic idea is to measure the ing. There were many stories of his col development so that now major results in individual particIe’s position at one point leagues being stuck with the apparatus, elementary particle physics appear to be and then convey this information along a until he arrived and rapidly solved thc prob coming from Europe instead of the USA, as chord ofthe accelerator ring so that correc lem. For the pp collider he became spokes previously. The experimental discovery of tions can be made when the information man forthe UAl collaboration of some 130 thc W and Z particles will live long in sci reaches thc far end of the chord at the same from Aachen, Annccy, Birming ence textbooks as an outstanding milestone time as the particle. This works even though ham. CERN, Harvard. Helsinki, Kiel. in the history of science thc signal from each antiproton is drowned Ouecn Mary College (London). Amster in the perturbation caused by the other par dam. College de France. Riverside, Rome, ticles. Van der Meer explains that a way of Rutherford Appleton Laboratory, Saclay, understanding how this concentrates the Vienna and Wisconsin. A key clcmcnt in antiprotons without violating Liouville`s the great success of their experiment is the theorem is to consider each particle as a large central detector which allowed indi Dr Douglas R () Morrison is in the Experimen point surrounded by empty space. The vidual tracks to be followed in a bubble tal Physics Division at CERN. Geneva

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