|Part of the Fermilab atom smasher.|
image: Fermi National Accelerator Laboratory
Scientists have long wondered just what it is that gives form to everything in the universe, from the computer screen in front of you to planets and stars. They have a theory about what it is, but they have yet to prove it.
The theory calls for the existence of a particle known as the Higgs boson, which is thought to be responsible for the mass of all matter. And while no one has been able to detect this elusive entity, the multi-billion dollar worldwide race to find it looks like its nearing the finish line.
We know youre in there...
Why are scientists searching so fiercely for something that exists only in theory? Because they know its there. There has to be some explanation to account for mass, without which the particles that make up matter would have nothing to hold them together.
That something has been dubbed the Higgs field, an invisible field that fills the universe and interacts with particles as they move through it. "The Higgs field creates weight, and without weight there is no stability and no form," says Leon Lederman, winner of the 1988 Nobel Prize in physics. "Without this field wed fly off the Earth and the Earth wouldnt revolve around the sun." The Higgs boson is so important that Lederman has called it "the God particle."
The Higgs boson got its name from Peter Higgs, a Scottish physicist who postulated its existence in the 1960s.
By way of explaining how the Higgs works, Lederman offers a metaphor in which water plays the role of the Higgs field: "Running on a dry beach you could run very fast, but if you are running in the water up to your knees, youre slowed up. If the water goes up to your neck, youre even much more slow, so the deeper the water, the heavier you are. The Higgs field is represented by the water slowing particles up."
There are four known forces in nature and the Standard Model of Quantum Theory deals with three of themelectromagnetism, the strong nuclear force, and the weak nuclear force. (Gravity, the fourth force, is not part of the Standard Model. When gravity is added to Standard Theory it is called Grand Unified Theory.) All of them are created or carried by sub-atomic particles (for instance, the electromagnetic field is carried by photons). A particle is therefore an indicator of a field, and the Higgs is no exception, Lederman explains.
"If we can find these [Higgs] particles in our super microscopes called particle accelerators, we can study its properties and really be on the way to perhaps a complete explanation of the big bang and how the universe evolved," he says.
|Part of the accelerator|
image: Fermi National Accelerator Laboratory
That is exactly what scientists have been trying to do for the past ten years. But trying to detect the Higgs boson is difficult because they have to first free it from the Higgs field and then detect it in the small fraction of a second it exists before decaying into other particles.
To do that, researchers at the CERN particle physics laboratory in Switzerland and the Fermi National Accelerator Laboratory near Chicago use a particle accelerator, commonly called an atom smasher. "An atom smasher is a machine like a microscope which produces a huge amount of energy in a very, very small space," explains Lederman. "Because of that production of energy you make particles and you can study them. By studying them you learn how the world works."
A few months ago, researchers at CERN thought they may have detected traces of particles that could be Higgs bosons with the Large Electron Positron Collider (LEP). But the results were inconclusive and the LEP was shut down in November to make way for what will become the worlds most powerful atom smasher, the Large Hadron Collider (LHC). It wont be operational until 2005, however.
Until then, the task of detecting Higgs has fallen to Fermilab, which has an accelerator known as the Tevatron. Although not as powerful as the LHC, it is currently the only accelerator in the world capable of detecting the Higgs, which it may very well do before the LHC has a chance to get started.
If either of these accelerators delivers the goods in the next few years, as they are expected to, the last remaining piece of the Standard Model puzzle may fall into place. Without the Higgs, or something like it, the Standard Model falls apart because it isnt able to accurately predict what happens to particles at very high energies and it doesnt account for gravity.
The Higgs boson is looked to not only as the glue that will hold the Standard Model together but as something that may prove other theories in particle physics as well. The supersymmetry theory, for example, which does hold up at high energies, calls for the existence of a partner for each particle type. This would mean there are twice as many particles as physicists have seen thus far. Like the Higgs, these particles are heavy and would only be detectable by the new generation of powerful particle accelerators like the Tevatron and the LHC. Detecting the Higgs might also pave the way for proving string theory, which unifies all the forces, including gravity.
So, the Higgs boson seems to be the gateway to an explanation of how the universe works. Lederman echoes the sentiments of many physicists when he says that "finding the Higgs particle would be a major deal."
Elsewhere on the Web
Explore the Atom
More on the Higgs boson
Particle accelerators around the world