Beguiling dark-matter signal persists 20 years on

By Davide Castelvecchi

A group of physicists says that it is still detecting the presence of dark matter — the mystery substance thought to make up 85% of matter in the Universe — 20 years after it saw the first hints of such a signal.

DAMA, a collaboration of Italian and Chinese researchers, has announced long-awaited results from six years of data-taking, which followed an upgrade to the experiment in 2010. The findings are a boost for the multiple groups attempting to reproduce DAMA’s results, which have been controversial and contradict those of other experiments. But DAMA’s improved sensitivity also makes its results harder to explain, physicists say.

Observations of galaxies and of the Universe’s primordial radiation imply that the vast majority of matter is of a type that is invisible and interacts almost exclusively through gravity. Many theories exist for explaining the nature of this dark matter, and lots of experiments have been attempting to detect it via subtle interactions with ordinary matter.

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