Dark matter is proved, Italian physicists say

Their team repeats an earlier experiment and finds consistent results, but critics say its claims are still questionable.

By Thomas H. Maugh II
Los Angeles Times Staff Writer

April 19, 2008

An Italian team on Wednesday renewed its claim to have discovered evidence for the existence of dark matter, the invisible material that makes up the bulk of the universe.

Critics say the University of Rome team has answered some of the objections to their earlier findings but not all of them, leaving their claims still a subject of great controversy.

"This is a Nobel Prize-winning result if it is proved," said physicist Richard Gaitskell of Brown University, who was not involved in the research. "But it needs to be confirmed, and the experiment really has to demonstrate a total mastery of the data. Neither of those criteria have been achieved, and therefore you have to bring a healthy skepticism to the result as it stands."

The dark matter in question is called weakly interacting massive particles, or WIMPs. Even though these dark-matter analogs of conventional particles are thought to be much larger than their visible-matter counterparts, they rarely interact with the visible world -- making their detection extremely difficult.

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