While CERN started as a European project, the sheer expense of the Large Hadron Collider, alongside the cancellation of its American rival, the Superconducting Supercollider, made it, notes Geoff Brumfiel, ‘the first truly global experimental undertaking’. n 1994, Britain and Germany had considered pulling out of the project. To rescue it, some of CERN’sleading scientist, including accelerator designer, Lyn Evans and the Director General Christopher Llewellyn Smith had persuaded CERN’s European council to accept a reduced design, and, in 1995, had persuaded Japan and Russia to fill the gap. India and the United States joined too.
So “beam day”, the first time protons had been coaxed around the full LHC ring, 10 September 2008, was a global news event. The Times of India reported on how scientists had gathered in great excitement at the Tata Institute of Fundamental Research (before a data link crashed leaving them in darkness), while the Economic Times of Indianoted with pride how 200 Indian scientists were involved, as well as a lucrative concrete contract. Israeli press reported the words of Prime Minister Ehud Olmert:”I’m very proud of the contribution made by the Israeli scientists and Israeli technology to an experiment of such magnitude, one that has the power to impact all of humanity”. ‘Scottish firm expands on Cern successes’ was a headline in The Scotsman. And so on.
So there was a measure of global embarassment when, nine days later, a cable linking two of the LHC’s magnets lost superconductivity, melting almost instantaneously. Liquid helium then leaked into the LHC tunnels. The whole $4 billion project was suspended for a year while the fault was fixed. Racks of computers, poised to store petabytes of information, sat unused. With no data, scientists across the world, including students waiting to finish PhDs, had no choice but to wait.
The LHC was designed to collide protons with antiprotons at energies seven times that of its nearest comeptitor, Fermilab’s Tevatron, and to search among the remnants for clues of physics beyond the standard model. With the the LHC out of action, scientists with alternative schemes of generating such physics suddenly had a window of opportunity. The Tevatron was cranked up as high as it would go, with each new collision added to a slowly building statistical picture, hinting at anomalies (such as in the decay of the strange B meson) that might not be explained by the standard model.
A second approach was to investigate the ghostly neutrino particles. In 1998, Japanese scientists using the Super-Kamiokande experiment in Hida, had shown that neutrinos switched between different types. This switching was only possible in neutrinos possessed mass, albeit a tiny one. (This finding had also resolved a long-standing and increasingly worrisome observation of a shortage of solar neutrinos.) Massive neutrinos were not part of the standard model. New, even bigger neutrino experiments, such as IceCube, an array of detectors under the Antarctic ice, it was hoped in 2008, might reveal new phenomena.
Finally, while the standard model is a theory of the fundamental forces of the universe, and usually probed at the microphysics level, it is also central to cosmological theory. Cosmologists had already noted a deficit between the observable matter in the universe and the deduced mass necessary for cosmologicaltheory to work. This deficit, labelled dark matter, was of an unknown nature in the first decade of the twentieth century. Neither had a candidate material been observed nor did the standard model have room for it. Yet dark matter was necessary to make sense of the speed of rotation of galaxies, and make up some 85% of matter in the universe.
Dark matter was the target of several large-scale scientific projects. In 2008, scientists working with data from a satellite called PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics, an Italian-Russian-German-Swedish collaboration) reported an unexpected amount of antielectrons of certain energies. Did they come from colliding exotic dark matter particles, such as the “neutralino”? Also in 2008, an underground dark matter detector at the Italian Gran Sasso National Laboratory also reported a signal. Yet other detectors, including ironically another one under the same Italian mountain, have seen nothing.
These non-particle accelerator routes to new physics may well become typical. The LHC is expected to last twenty years – if it works. The machine that the global fundamental physics community regards as the successor to the LHC – an electron-positron collider called the International Linear Collider – barely limped on as design money was cut and partner countries, such as the United Kingdom in 2008, pulled out.
In contrast to stalling and uncertain experiments, theory scored an impressive goal in 2008 in a highly-precise demonstration, published by Stephan Dürr et al in Science, that the predictions of mass made by the theory of quantum chromodynamics (QCD) matched observed masses of hadrons very closely. Frank Wilczek in Nature praised the achievement, both for its practical implications (understanding for example, supernovae) and as a triumphant vindication of the Pythagorean credo that “all things are number”. ‘The accurate, controlled calculation of hadron masses is a notable milestone’, the theoretical physicist wrote, ‘But the fact that it has taken decades to reach this milestone, and that even today it marks the frontier of ingenuity and computer power, emphasizes the limitations of existing methodology and challenges us to develop more powerful techniques’. An alternative way of putting this would be that theory, too, had trouble scaling up.