Physicists May Have Found Elusive 'Higgs' Particle
By K.C. Cole
Los Angeles Times
GENEVA - For more than 20 years, scientists around the world have been searching for an invisible particle that determines the basic properties of matter. The particle, called a "Higgs boson," is thought to be a vibrating chunk of the unseen vacuum that underlies everything in the universe.
Physicists at the European laboratory CERN are set to announce what they believe is the first glimpse of the Higgs boson.
The evidence is by no means conclusive. But the discovery of the Higgs boson is considered critical to physics - not only concluding one chapter but opening the door to another completely undiscovered realm.
"The Higgs is not just a particle," said CERN theorist John March-Russell. "It means there's this whole new world out there."
Once physicists understand this pervasive, unseen influence, they will be able to answer a question so fundamental that ancient thinkers probably never even dared to ask it: "Why does matter have mass?"
Said Princeton experimentalist Chris Tully: "I think it will eventually be hailed as one of the greatest achievements you can make in science."
Possible traces of the long-sought particle were detected in experiments in the 17-mile-around Large Electron Positron collider, or LEP, by crashing atomic particles at high speeds.
Tracks suggesting the possible presence of the so-far unseen Higgs have teased CERN physicists with a frustrating succession of appearances and disappearances over the past month. But evidence accumulated last week finally convinced the experimenters to request an emergency resuscitation of the aging accelerator. CERN officials had previously decided to tear down the collider and start construction on a replacement.
"It's a very pleasant emergency," CERN director general Luciano Maiani, who has been a confirmed skeptic, told the Los Angeles Times, "Last week changed everything."
The final decision on the fate of the collider awaits a vote by CERN's 20 member states, probably next week. But for the time being, it looks like the hordes of workmen waiting with "blow torches and axes," as one physicist put it, to dismantle the machine will have to go home.
Skeptics have been saying for weeks that the hints that surfaced at CERN last month were only wishful thinking - a desperate attempt to claim a prize that almost surely would have gone to the rival Fermilab outside Chicago, had CERN's accelerator shut down.
The skeptics had a very good case: out of four cathedral-sized electronic "eyes" that watch for the Higgs, only one had seen the telltale tracks. A few weeks later, another detector saw something, only to have the evidence evaporate under future scrutiny.
In a dizzying series of events since mid-October, however, two other detectors at the collider spied what scientists feel are solid Higgs tracks.
"Among physicists, we believe we have them. But we don't believe we have enough of them (to claim a discovery)," said Jason Nielsen, a graduate student from the University of Wisconsin.
So after a week of sleepless nights and tense hallway conversations, Maiani has decided to ask for a reprieve.
It won't come cheaply. In addition to about $70 million to pay off contractors standing by to destroy the LEP collider and build the next machine, it will take a big toll in careers disrupted and personal plans put on hold.
Normally, the physicists wouldn't have even gone public with their findings until physics conferences next spring, said physicist Tiziano Camporesi. "But by next spring, the detector would be gone."
Why all the fuss? The answer is that the vacuum of physics gives structure to everything else. Like the strings of an unseen puppeteer, it holds all matter under its influence.
The Higgs field is a fundamental part of this nothingness. It's like water to a fish, an essential ingredient of the universe. And the Higgs boson has enormous consequences: Without this hidden field, all particles would travel at light speed. Atoms could not exist.
Often described as a kind of cosmic molasses, the Higgs changes the properties of particles that travel through it. It imparts a kind of sluggishness, or mass. Until recently, mass was considered so basic a property of matter that scientists didn't even think it ask where it came from. "It was God given," Maiani said.
How can the physicists see the vacuum? The same way a brick "sees" the Earth when it falls to the floor, or a magnet "sees" metal. The unseen influence affects the way things move. In fact, the very observation that things have mass confirms the Higgs exists, physicists say.
To prove their theories, however, they need to set the vacuum vibrating with enough energy to send a chunk of it, in effect, "free." Only that way can they study its properties.
The CERN machine accomplishes the feat by colliding two beams of particles head on at enormous energies. Electrons circling in one direction meet their anti-matter counterparts, called positrons, circling in the opposite direction at four intersections along the accelerator ring.
All that energy goes into mutual annihilation - a burst of pure energy.
And out of that ball of energy comes new particles. If the physicists at CERN are right, their collisions have produced a so-called Z particle, massive enough to set the vacuum twanging for a tiny fraction of second and produce the Higgs boson.
Alas, the Z and the Higgs both dissolve into other particles before traveling even a few inches at nearly light speed.
Therefore, the details of the collision must be inferred by the tracks left in the four detectors placed at the intersections of the particle beams. As pieces fly out from the site of the collision, every stray bit is identified, tracked and counted.
Buried in pits hundreds of yards under the rolling French countryside, these enormous, tinker toy-like detectors operate in ways surprisingly similar to human eyes: After collecting detailed information on properties of particles that pass through - speed, electric charge, mass and so forth - they make what amount to intelligent "guesses" on what they "see."
At the end, what they have is a carefully measured probability of being right.
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