Munich

Switched off: accelerating cavities from the soon to be dismantled LEP collider in Geneva. Credit: CERN

After eleven years and a nail-biting three-month reprieve, the death knell for the Large Electron–Positron collider (LEP) in Geneva has finally been sounded.

Last week, Luciano Maiani, director-general of CERN, the European Laboratory for Particle Physics, rejected requests to keep the LEP running for another year, ruling that it should be dismantled early in the new year as planned.

The drama over the collider's future centred on the possible sighting by the LEP's detectors of the subatomic particle known as the Higgs boson (see Nature 408, 10; 2000). Showing that Higgs exists would bolster the Standard Model of particles and forces, and fulfil one of CERN's major missions.

The LEP had been granted a one-month extension to gather more data in support of the initial observation. As the probability that Higgs really had been seen fell at first, only to rise in the past few weeks, pressure grew on CERN's management to keep the LEP running for another year.

But that would have cost SFr100 million (US$57 million) and delayed construction of the Large Hadron Collider (LHC), which will be powerful enough to confirm the Higgs if, as the LEP experiments suggest, it has a mass of 115 giga-electron volts.

High-energy physicists were unable to reach a consensus on whether the risk should be taken. The LEP scientific committee comprising LEP researchers, including some with experiments planned for the LHC, split 50–50 on whether to recommend the extension to CERN's research board. The board, whose job is to balance the whole of CERN's programme, also failed to reach a consensus. Even appeals to CERN's external Scientific Policy Committee drew an inconclusive response.

That left Maiani to bear responsibility for the decision. He took it, he says, not on a financial basis, “but on the basis of optimizing the overall scientific return of the laboratory”.

“The conclusive discovery of Higgs within a year was not guaranteed and I thought it too risky to delay the LHC and distract the scientists who are going to run its experiments,” he says. The LHC will, Maiani points out, let physicists study the properties of Higgs as well as just identifying it.

Roger Cashmore, CERN's research director, adds: “The best way forward for CERN is to proceed with the LHC as fast as possible. To change a good research programme you need a very strong set of arguments, which the committees did not supply.”

But Chris Tully, one of the CERN physicists who worked on the Higgs search data, says the decision is “tragic for CERN”. He believes CERN management has underplayed the strength of the evidence that the Higgs has been sighted.

→http://public.web.cern.ch/Public