Racing to the 'God Particle'

Physicists from all over the world are racing to prove the existence of a particle that's surmised to be at the heart of the matter. Literally!

Dubbed the "God particle" by Nobel Prize-winning physicist Leon Lederman, the Higgs boson is a controversial particle believed to bestow mass on all other particles.

Scientists are hoping to discover traces of its presence in Fermilab's Tevatron, a 7-mile-long circumference particle accelerator that smashes opposing beams of protons and antiprotons around a circular track, sifting through the debris with two immense detectors called CDF and D0, because it plays a key role in the standard model of physics (the theory on which physicists base their whole understanding of matter), proving the existence or absence of the Higgs boson could rock the entire foundation of physics, indicating the existence of particles and forces not yet imagined and paving the way for an entirely new set of laws.

The Higgs boson is interesting because it is the only reasonable explanation we have for the origin of mass," says Dave Rainwater, a researcher at FermiLab.

"Without the Higgs, all fundamental particles would be massless, and the universe would be very different. The weak nuclear forces wouldn't be weak at all, for instance, so the elemental composition of the cosmos would be radically different, stars would shine differently, and we probably wouldn't exist."

The best experimental data on the Higgs boson so far comes from experiments done with the LEP collider at CERN, near Geneva, in 2000. Results indicated that the Higgs particle was too heavy to be detected by the collider and that it probably had a mass of 114 billion electron-volts (GeV). The Tevatron is expected to be able to spot the Higgs in a couple of years, if it is not heavier than 170 GeV to 180 GeV.

If all else fails, the Large Hadron Collider being built at CERN, scheduled to go online in 2007, is designed to guarantee discovery of the Higgs. With a 27-kilometer-circumference tunnel, the LHC will collide protons at seven times the energy levels of the Tevatron.

And the payoff for whoever discovers the Higgs boson? Nothing less than a Nobel Prize. "Its discovery would be one of the crowning achievements of modern science, and validate decades of intense research," says John Conway, a professor at Rutgers University.

"We believe that the Higgs is the key to unlocking the mystery of the elementary particles: the quarks and the leptons. The standard model does not give us the answers to many questions: Why are there three 'generations' of matter particles? Why do they have the masses and electric charges that they do? The Higgs is believed to be related to the mechanism by which the matter particles get their mass, but there is no good theory yet as to why different particles have different masses."

"One thing we expect the Higgs to open up is the question of supersymmetry," says John Womersley, co-spokesman of the D0 experiment at Fermilab.

"Supersymmetry is a relationship between the particles of matter and the forces of the universe. Mathematically, it's beautiful. Not one piece of direct experimental data really supports it yet. Finding a Higgs in the place we expect would be a piece of evidence. Not finding it would be a big problem for the advocates of this idea.

"What would shake the foundation of physics much more than finding the Higgs would be a definitive
'ruling it out.' That would upset all of our conceptions about how the universe works. It would make supersymmetry something that, if it applies in the universe, does so only at much higher energies than we can observe. And it would require new forces or new laws to explain masses, in the absence of a Higgs."

The last stage in this three-stage relay race is a linear collider. While the LHC is guaranteed to make a definitive discovery or exclusion, it will not be able to measure the properties of the Higgs precisely. "There is an international consensus among the particle physics community that we would need another accelerator to go one step beyond and resolve the riddles ... nature gives us, (of) which we will have first insights from the Tevatron and the LHC," said Dr. Klaus Desch, a scientist at the University of Hamburg who is working on the European study for such a machine called TESLA.

"The linear collider will enable us to actually verify that the Higgs has exactly the properties we expect. We'll be able to test that it couples to each particle proportional to the mass," added Womersley.

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