Massive discovery?

CERN scientists think they have spotted the Higgs particle, the most sought-after prize in particle physics 

PHYSICISTS think they've caught tantalising glimpses of the elusive particle that gives matter its mass.

Researchers working with a giant particle detector called ALEPH at the CERN particle physics laboratory near Geneva say a handful of oddball collisions may mark the fleeting appearance of the Higgs boson. The Higgs is a crucial piece in the jigsaw of fundamental particles. Finding it is currently the big prize for particle physicists.

The machine that produced these events, the Large Electron Positron Collider (LEP), is scheduled to close down for good at the end of this month. So the ALEPH researchers have precious little time to collect enough data to confirm their observation.

Without the Higgs boson, or some more convoluted explanation, the Universe as we know it wouldn't exist. Postulated more than 30 years ago, the Higgs gives particles such as quarks and electrons their mass. Particles swim through a sea of hidden Higgs bosons, which drag on them and produce inertia, the essence of mass.

Physicists have been searching for the Higgs for more than a decade. Although Higgs particles are extremely massive, they are normally hard to spot because they exist only "virtually". Higgs particles exploit the inherent uncertainty in quantum mechanics to pop in and out of existence for only the briefest of instants, too short a time to be observed.

To see a Higgs, physicists have to manufacture one by smashing extremely fast-moving particles together. The energy of the collision is converted into matter, and if the energy is high enough a bona fide Higgs may pop into existence. Having done so, it decays into a telltale combination of other particles.

Such decays could account for several unusual events observed recently at LEP, ALEPH researchers said this week at a meeting at CERN. But they admit that their evidence is not yet conclusive. "It's unfortunately not enough to say we have made a discovery," says ALEPH's Wolf-Dieter Schlatter.

It's possible that the events are chance combinations of random particles, or fakes produced by familiar particles such as Z bosons decaying in just the right way to mimic a Higgs. Such explanations are made more likely by the fact that none of the other 3 particle detectors arrayed around LEP has seen any sign of Higgs events.

The question is whether CERN should keep LEP running to try to confirm the Higgs sighting. ALEPH researchers could double their data if LEP ran until the end of the year.

The 27-kilometre-long LEP, housed in a ring-shaped tunnel straddling the Swiss-French border, has already painted detailed portraits of the W and Z bosons, and has proved that there can be no more than six quarks. It is due to be dismantled to make way for a new machine in the same tunnel, the Large Hadron Collider, scheduled to begin hunting for the Higgs particle in 2005.

In the meantime, CERN's great rival, Fermilab near Chicago, may find the Higgs first. Fermilab will resume colliding beam experiments this month, after more than four years of renovation.

Some think the ALEPH team may be making too much of too little. "You wonder if it's just a way for them to extend their running time," says Dave Besson of the University of Kansas in Lawrence. ALEPH collaborator Alan Litke rejects this suggestion. "We have no interest," he says, "in running LEP for the sake of running LEP". 

Adrian Cho (newscientist.com)  -  Back to the start

 

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