Particle May Be Leading Candidate For Mysterious Dark Matter
Physicists may have glimpsed a particle that is a leading candidate for mysterious dark matter but say conclusive evidence remains elusive.
A 9-year search from a unique observatory in an old iron mine 2,000 feet underground has yielded two possible detections of weakly interacting massive particles, or WIMPs.
But physicists, who include two University of Florida researchers, say there is about a one in four chance that the detections were merely background noise - meaning that a worldwide hunt involving at least two dozen different observatories and hundreds of scientists will continue.
"With one or two events, it's tough. The numbers are too small," said Tarek Saab, a UF assistant professor and one of dozens of physicists participating in the Cryogenic Dark Matter Search II, or CDMS II, experiment based in the Soudan mine in Northern Minnesota.
A paper about the results is set to appear February 11 in Science Express, the journal Science's Web site for selected papers that appear in advance of the print publication.
Scientists recognized decades ago that the rotational speed of galaxies and the behavior of galaxy clusters could not be explained by the traditional forces of gravity due to the mass of visible stars alone. Something else - something invisible, undetectable yet extremely powerful - had to exert the force required to cause the galaxies' more-rapid-than-expected rotational speed and similar anomalous observations.
What came to be known as "dark matter" - dark because it neither reflects nor absorbs light in any form, visible or other - is now estimated to comprise as much as 23 percent of the universe. But despite abundant evidence for its influence, no one has ever observed dark matter directly.
There are several possibilities for the composition of this mysterious, omnipresent matter. Particle physics theory points toward WIMPs as one of the most likely candidates.
"Closeup of a CDMS detector, made of crystal germanium. (Credit: DOE/Fermi National Accelerator Laboratory)"
Source: University of Florida
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