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Search for Higgs is hot, not heavy: new data indicate lower mass is probable for elusive particle.

The God particle has fewer places to hide.

New data offer evidence that the heft of the Higgs boson lies in the low end of the range being probed by particle colliders on two continents.

The new result comes from two ongoing experiments at the Fermi National Accelerator Laboratory's Tevatron accelerator in Batavia, Ill., suggesting that the elusive Higgs does not have a mass between 158 billion and 175 billion electron volts. (A billion electron volts, or 1 GeV, is slightly heavier than the mass of a proton.) Ben Kilminster of Fermilab reported the result July 26 in Paris at the International Conference on High Energy Physics, and a paper was posted online at arXiv.org.

Studies from the Large Electron-Positron Collider, which shut down in 2000 at the European research organization CERN, along with indirect constraints, had indicated that the Higgs could weigh in anywhere between 114 and 185 GeV. In late 200% the two Tevatron experiments, known as CDF and DZero, excluded the range between 162 GeV and 166 GeV. The new data have ruled out nearly 25 percent of the mass range for the Higgs allowed before 2009.

Dubbed the God particle because it would explain why some subatomic particles have mass, the existence of the Higgs was proposed in 1964 by physicist Peter Higgs, who posited a quantum field pervading the vacuum of space. The field would slow down some particles traveling through it, causing them to acquire mass. Other particles, like photons, would be impervious to the field and continue to travel at the speed of light. Although the field couldn't be detected directly, it could be excited at high energies to produce the Higgs particle.

The new limit on the particle's mass "is important, as it demonstrates the power of the Tevatron experiments to search for the Higgs," says theorist JoAnne Hewett of the SLAC National Accelerator Laboratory in Menlo Park, Calif. "They just keep getting better and better."

However, Hewett notes, excluding the region from 158 to 175 GeV for the mass of the Higgs won't have much effect on theory, because most physicists expect the Higgs to be lighter than 135 GeV.

The latest analysis of data recorded by Tevatron's CDF experiment has turned up intriguing hints of a 140-GeV Higgs, Abid Patwa of the Brookhaven National Laboratory reported at ICHEP on July 23. That development "has the theory community abuzz," Hewett says.

CDF cospokesman Rob Roser of Fermilab says, "We see something. It could be consistent with many things," including a low-mass Higgs. "I am not sure I would agree that 'the community is all abuzz,' but perhaps the theorists are excited--they are an excitable lot."

Narrowing the Higgs hunt

Combined data from two experiments at Fermilab's Tevatron particle accelerator indicate that the elusive Higgs boson does not have a mass between 158 and 175 billion electron volts.

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Title Annotation:Atom & Cosmos; Higgs boson
Author:Cowen, Ron
Publication:Science News
Geographic Code:1USA
Date:Aug 14, 2010
Words:479
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