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Have their eyes seen 'God particle'? Fermilab finds hints of Higgs boson

July 02, 2012|By Amina Khan, Los Angeles Times / For Science Now
  • The Compact Muon Solenoid detector at the Large Hadron Collider is a key experiment in efforts to validate a long-held theory of particle physics.
The Compact Muon Solenoid detector at the Large Hadron Collider is a key… (CERN )

As physicists prepare to announce highly anticipated results concerning the elusive "God particle" on Wednesday, scientists in the U.S. announced Monday that they’ve found evidence for the existence of what’s known as the Higgs boson.

Researchers at the Fermilab Tevatron accelerator near Batavia, Ill., have pulled together their final findings in the search for the elusive Higgs boson. Their announcement comes just two days before scientists using the powerful Large Hadron Collider at the European particle-physics center CERN plan to unveil highly anticipated results from their high-energy, proton-smashing experiments.

The Higgs boson is thought to give other elementary particles their mass. It is the only such particle predicted by the Standard Model of particle physics that has yet to be observed -- and it’s fundamental to our understanding of the universe, scientists said.

GRAPHIC: How the Large Hadron Collider works

“We think the Higgs boson really gets at the center of some physics that is responsible for why the universe is here in the first place and what the ultimate structure of matter is,” said Joe Lykken, a theoretical physicist at Fermilab.

The Internet was abuzz with rumor and speculation Monday afternoon as reports surfaced that the scientists might not definitively confirm the boson’s existence Wednesday, or might even announce an entirely new particle, according to Nature. Four of the theorists who came up with the Higgs mechanism half a century ago will also reportedly be present.

The universe, the theory goes, is permeated by what’s known as the Higgs field.

“You can think of it as an energy field. We believe there is a Higgs energy field spread out in the whole universe,” Lykken said. Photons -- light particles -- are unaffected by this field. But as other elementary particles move around, he explained, “they feel this energy field as a kind of sticky molasses that slows them down and keeps them from moving at the speed of light."

When enough of that field is packed into a small enough space, Lykken said, it manifests as a particle -- the Higgs boson.

But these kinds of elementary particles are exceedingly difficult to create and detect -- they require high-energy collisions, and then they break down into other particles a mere instant after forming. Scientists often look for the particles created by their decay. And just as a dollar can be broken down into four quarters, or 10 dimes, or 95 pennies plus a nickel, the Higgs boson can break down into many different combinations of particles -- it’s just a matter of figuring out what exactly those combinations are.

The Tevatron researchers looked for the Higgs particle by looking for one combination of this subatomic coinage: a pair of bottom quarks. Scientists at the Large Hadron Collider look for two energetic photons to catch the Higgs purported signature.

But even though these energetic photons are thought to provide some of the clearest ways to search for a Higgs boson, it's still incredibly difficult to pick out a signal from all the "noise" around it.

One major problem is that, up until now, the scientists don’t know the Higgs boson’s mass. To extend the money metaphor: They don’t know whether they’re looking for the change from a one dollar bill or a fiver, or some amount in between. The Tevatron findings, however, appear to have narrowed that window of possibility.

Though the Tevatron ceased operations last fall, researchers have pulled out a few more useful results from the 500 trillion or so collisions the particle accelerator produced since March 2001. They were able to determine, for instance, that the Higgs boson -- if it exists -- weighs in somewhere between 115 and 135 GeV/c2, or about 130 times a proton’s mass.

For the moment, though they have detected what they believe could be evidence of the Higgs boson, researchers have tried make their results as ironclad as possible, with a 99.99994% chance of being correct. It’s a benchmark known as 5-sigma, sometimes called the gold standard of particle physics. Current experiments have surpassed 4-sigma, which (at about 99.994% chance) is just a hair less certain.

Though it may seem like an infinitesimally tiny distinction, this kind of hair-splitting makes a world of difference to scientists, eagerly awaiting Wednesday’s announcement.

Describing their state and appearance at a Fermilab news conference Monday morning, Lykken said, “This is what physicists look like when they’re excited. And also missing quite a few nights of sleep, I would imagine.”

Follow me on Twitter @aminawrite.

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