Scientists Closer To Solving Dark Matter Mystery

Tuesday, September 14, 1999

By Patricia Reaney

SHEFFIELD, England (Reuters) - Scientists said Tuesday they could be closer to understanding the mysterious subatomic particles that may make up the dark side of the universe.

Physicists believe so-called Weakly Interactive Massive Particles (WIMPs) could account for the 90-99 percent of the universe's dark matter which cannot be seen because it does not emit light.

One theory is that the dark matter consists of subatomic particles, so far undiscovered, that were produced in the Big Bang scientists say started the Universe. The particles, or WIMPS, fill space and hold the galaxies of stars together. With the help of ultra-sensitive detectors Sheffield University's Dr. Neil Spooner and his team have found ''intriguing'' signals in Europe's deepest salt mine, the Boulby mine, which they say could be the first signs of WIMPs.

``So far we have no explanation for them,'' Spooner told a news conference at a British science congress.

``The question one would ask is 'have we found WIMPS?' and the answer is 'not yet', but definitely these things are unexpected events...interestingly, another group has seen similar events at a similar rate so we're excited about this and have spent a long time investigating it,'' he added.

Spooner said there were two possible explanations. Once was that the signals could be the result of a problem in an instrument.

``The other explanation is that we haven't ruled out the possibility that we have seen something,'' he added.

Spooner hopes further work and more advanced detectors may help solve the puzzle.

The scientists chose an underground location for their experiments because if the detectors had been on the surface at ground level, they could have detected other particles ranging from cosmic rays to natural radioactivity.

To see a WIMP, the underground detectors must be surrounded by a shielding material, which in northern England's Boulby mine is distilled water. The mine's depth blocks the cosmic rays and the water stops the natural activity of the rock.

Scientists say there is black matter because without its gravitational influence the universe would not exist.