Nobel prizewinner in 1984, architect and mason of CERN’s biggest ever physics discovery and director-general of CERN from 1989 to 1993, Carlo Rubbia remains a continual fountainhead of new ideas. A recent seminar at CERN highlighted the extent of his work.
CERN owes a tremendous debt to Carlo Rubbia. His vision foresaw a gleaming new SPS proton synchrotron transformed into a proton antiproton collider, the springboard for discovering the W and Z particles, the carriers of the weak force. With this discovery, CERN moved to the centre of the world physics stage. At a special seminar at CERN on 16 March, director-general Luciano Maiani pointed out that Rubbia’s vision brought the W and Z particles into the reach of physics much earlier than would otherwise have been possible.
The birthday seminar focused on science, but CERN’s debt to Rubbia extends much wider. When he took over from Herwig Schopper as CERN director-general on 1 January 1989, the LEP electronpositron collider had not yet come into operation, research and development work on superconducting magnets for the proposed LHC proton collider was just beginning, and CERN had 14 Member States: Austria, Belgium, Denmark, France, the German Federal Republic, Greece, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the UK.
The LHC road had already been chosen in 1986 as the main thrust of CERN’s scientific advance by the CERN Long Range Planning Committee, chaired by Rubbia. The route to higher electronpositron collision energies through a purpose-built linear collider (CLIC; CERN Linear Collider) was also acknowledged at that time.
Under Rubbia, the LHC moved from a proposal to a plan, with orchestrated research and development in CERN, other laboratories and industry. In parallel, the LHC’s proposed research programme emerged from a vigorous and carefully managed series of presentations throughout the world.
To safeguard CERN’s future and reflect the growing internationalism of high-energy physics, Rubbia sought to extend CERN’s traditional role as a Western European venture by attracting new member states in Central and Eastern Europe, and by negotiating valuable new working agreements with scientific partners further afield.
Finland, Poland, Hungary, the Czech Republic and Slovakia became CERN member states, while Germany grew to include the former German Democratic Republic, and CERN’s relations with other traditional close collaborating nations, notably Russia and Israel, were put on a new footing.
Rubbia worked tirelessly to ensure that LHC plans moved steadily forward during a global recession, when money was extremely tight and governments were not looking at pure science as an investment for the future.
A life in science
Scientific research has dominated Rubbia’s life, and the seminar emphasized this side of his achievement, which was for a long time concentrated around weak interactions. Rubbia was also a transatlantic physicist, carrying out research at major US research centres as well as at every CERN machine (prior to LEP).
The seminar proceedings were introduced by 1992 Nobel prizewinner Georges Charpak, who pointed to Rubbia’s latest research interests around emerging energy technology as an example of his continual quest for innovation and his flair for new ideas. Innovative instrumentation has been a theme throughout Rubbia’s career.
Val Fitch of Princeton, who shared the 1980 Nobel Prize with Jim Cronin for their discovery of CP violation, described Rubbia’s contributions in this area of physics in the period 1966 to 1973. Fitch displayed a list of 20 physics papers and 4 instrumentation papers with Rubbia as an author, and which had helped to pin down vital parameters in these difficult measurements.
Klaus Winter of CERN looked at the neutrino sector. Rubbia was convinced that neutrino beams were the route to the discovery of the neutral currents the key to electroweak unification. In the early 1970s, he and his colleagues convinced the new Fermilab to make a major commitment to this physics. The experiment’s all electronic detectors bore the unmistakable stamp of Rubbia ingenuity.
After a long period away from the neutrino stage, the excitement around neutrino oscillations tempted Rubbia back, this time with the ICARUS neutrino detector at the Italian Gran Sasso underground laboratory. The innovative liquid argon time-projection chamber again bears the trademark of Rubbia innovation.
Turning away from the experimental side, Gerard ‘t Hooft of Utrecht sketched the development of the theoretical infrastructure that led to electroweak unification and the Standard Model, which Rubbia’s 1983 discovery dramatically confirmed. ‘t Hooft remarked that new theoretical ideas in and around superstrings have predictions that are very difficult to verify by conventional experiments.
Alan Astbury of TRIUMF, Vancouver, a close collaborator of Carlo Rubbia for the UA1 experiment at CERN’s protonantiproton collider, covered the historic period from the late 1970s that led to the 1983 discovery of the W and the Z particles. This physics was a continual close race between the UA1 and UA2 experiments. Astbury pointed out how UA1 had been galvanized into action in late 1982 by having lost the race to discover the tightly confined “jets” of particles, which signal quarkgluon interactions deep inside the protonantiproton collisions.
After his mandate as CERN director-general, Rubbia made a dramatic return to the physics stage, this time through his ideas for harnessing accelerators for energy production via nuclear fission with a minimum of nuclear waste and for the destruction of existing waste by transmutation.
Arthur Kerman was billed as covering this phase of Rubbia’s career, but began by pointing out the initial role Rubbia had played in recommending the US Superconducting Supercollider. Kerman described the neutron behaviour that opens up the possibility of controlled fission reactions, whether by orthodox absorbers or via an accelerator in tandem with the reactor. The latter possibility had long been recognized, but only recently has accelerator performance begun to approach the necessary levels.
Carlo Rubbia characteristically used the occasion to look forward rather than back, underlining how little we know about the universe. With much of the world around us composed of invisible but all-pervading “dark matter”, innovative instrumentation is still called for.
Finally director-general Luciano Maiani underlined the breadth of Carlo Rubbia’s contributions, both to CERN and to physics.