The legendary particle that physicists thought explained the basic question of why matter has mass, often called the ?God particle,? probably does not exist. Researchers who have spent a year analyzing data from the LEP accelerator at the CERN nuclear physics lab near Geneva, Switzerland say that the elusive Higgs boson, which is central to the theory on which physicists base their whole understanding of matter, does not exist. If there is no Higgs, they are totally unable to explain mass.
The current model of the universe says that a collection of fundamental particles make up matter, including muons, electrons, neutrinos and quarks. In the 1960s, researchers successfully worked out how these particles interact and bind with each other using strong and weak nuclear forces.
But that doesn?t explain why the particles also have mass. Then Peter Higgs of Edinburgh University suggested that space is filled with a heavy substance, now called the Higgs field, which gives particles their mass by dragging on them through a particle called the Higgs boson.
Thus began the 30-year quest to find the God particle. From interactions between other particles that we know exist, physicists calculated that the Higgs is most likely to have a mass (or energy) of around 80 gigaelectronvolts (GeV). If particle accelerators could smash particles together at that energy or higher, it would be possible to make one. This is what members of the Electroweak Working Group at CERN have been doing for the 5 years until LEP (the Large Electron Positron Collider) closed down last year. Since then they?ve been searching through the data they gathered, and they?ve found no sign of the Higgs boson. ?It?s more likely than not that there is no Higgs,? says group member John Swain of Northeastern University in Boston.
Last year researchers from another group at LEP claimed they had found the Higgs. Their announcement came shortly before LEP was due to close, and it got them one month?s extra time on LEP. But they later admitted their calculations were wrong.
Now their calculations have been reworked, and members of the Electroweak Working Group say there is no sign of the Higgs. Its existence is looking ?less and less likely,? says Steve Reucroft, also of Northeastern University. ?We?ve eliminated most of the hunting area,? adds Neil Calder of CERN.
Frank Wilczek, a particle physics theorist at the Massachusetts Institute of Technology, believes that the Higgs can be found only at an improbably high energy level. He says he?ll stop believing in the Higgs if it doesn?t show up by about 130 GeV. ?Then I would have a good long think,? he says.
Swain says he doesn?t think the Higgs exists. But he still thinks it?s important for CERN to build its Large Hadron Collider, which is scheduled to start smashing particles at even higher energies in 2007. ?It?s not until you’ve ruled out more than 99 per cent of values that everyone will be convinced,? he says.
The problem for physicists is that without the Higgs particle they don?t have a viable theory of matter. ?There is nothing remotely as plausible or compelling to replace it,? says Wilczek.
For physicists who have spent years trying to find the Higgs, admitting it may not exist is hard. But Swain is ready to move on and says, ?You search for the truth, and the truth is whatever it is.?
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