Published online 10 December 2010 | Nature | doi:10.1038/news.2010.667

News

LHC plans extra year for Higgs hunt

Collider may run right through 2012 to find elusive particle.

ATLAS cavern, installation of Muon chambersThe extra year could be enough for the ATLAS detector to spot the Higgs particle.Claudia Marcelloni / CERN

Scientists are preparing to run the world's largest particle accelerator for an extra year in a bold bid to find the Higgs particle, part of the mechanism that is thought to endow other particles with mass.

If the plan is implemented, the Large Hadron Collider (LHC), located at CERN, near Geneva, Switzerland, will run until the end of 2012 — rather than 2011 — before entering a year-long shutdown for a major upgrade. Preparations for the extended run, which would see the 27-kilometre circular collider operating over three continuous years, are being finalized and are likely to be agreed to by CERN's management and council in January.

The decision comes with the belief that new discoveries may be just around the corner. "It would be a shame to stop," says Steve Myers, who is responsible for maintaining and upgrading the accelerator.

“It would be a shame to stop.”

Steve Myers
CERN

At stake is the particle many physicists see as the LHC's raison d'être: the Higgs. Theorists believe that the Higgs particle, together with its associated field, create a sort of cosmic molasses that endows other particles with mass. The mechanism is seen as a necessary extension to the 'standard model' of particle physics, which presently struggles to explain the origins of mass, and why some particles are heavy whereas others weigh nothing at all.

Higgs hunt

Initially, there were doubts about whether the LHC would be able to find the Higgs at the machine's current energies. Since a major accident in 2008, the LHC has been running at half its design energy. CERN managers had planned a 15-month pause in data collecting at the start of 2012, which would allow the machine to be upgraded to full power.

But now there is a growing consensus that the LHC will be able to cover most of the territory in which a standard Higgs particle might be found, even if it isn't upgraded. The best guess of most physicists is that the Higgs weighs somewhere between 114 and 600 gigaelectronvolts (109 electronvolts), according to Sergio Bertolucci, CERN's director for research and computing. Its mass will determine how the particle decays — and how easily it can be detected.

“If we stop the machine with 3,000 people apiece in the experiments waiting for data, there is no way we could get home at night without having slashed tyres on our cars.”

Sergio Bertolucci
CERN

Paradoxically, a heavier Higgs might be easier to spot, Bertolucci says. That's because the heavy Higgs is likely to decay into pairs of rare, heavy particles known as W and Z bosons. Pairs of Ws or Zs would stand out sharply against the other particles created in LHC collisions. If the Higgs were lighter, its signature would blend into the background, making it much harder to detect and requiring physicists to amass and filter through data from months of collisions.

Despite the challenge, Bertolucci says that he is "very optimistic" that the LHC can cover most of the ground over which the Higgs is expected to be found. The machine has performed exceptionally well since the 2008 accident, and he thinks that it will be able to deliver the quantities of data needed over the 2011-12 running period. In addition, he says, managers think that they can collide particles at 8 teraelectronvolts (TeV; 1012 electronvolts), up from the current 7-TeV energies, but still well below the machine's 14-TeV design energy.

Pushing it

Physicists working on the detectors built to find the Higgs are backing the plan. "My personal opinion is that we should put all the cards on the table," says David Francis, a physicist on the ATLAS detector, one of two giant detectors primarily designed to spot the elusive particle. "The experiments are going well, the accelerator is going well," adds Joe Incandela, a physicist at the University of California at Santa Barbara and deputy spokesman for the CMS detector, the second main detector for Higgs hunting. "Let's really push it to where we can get a meaningful data set to do lots of physics."

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Bertolucci says that there are also political reasons to extend the run. The world's second most powerful accelerator, the Tevatron at Fermilab in Batavia, Illinois, is nipping at the LHC's heels, and if it continues to run, might beat the larger accelerator to the Higgs. Moreover, European plans for high-energy physics, as well as a global plan for a next-generation linear collider, are facing big decisions in the coming years and will be greatly influenced by the LHC's results.

But keeping the machine running for an extra year will have consequences. The delicate alignment of the LHC's superconducting magnets could suffer, requiring extra maintenance, says Myers. And additional computing resources will have to be found to handle the flood of extra data produced by the detectors.

Managers recognize the difficulties, but Bertolucci says they have strong incentives to extend the run: "If we stop the machine with 3,000 people apiece in the experiments waiting for data, there is no way we could get home at night without having slashed tyres on our cars."

The decision will be discussed at a meeting in the French town of Chamonix in late January, and should be finalized shortly after. 

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  • #60785

    While I understand the scientific implications such a discovery would have, would proof of the Higgs have any practical implications. Could such knowledge be used or applied?

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