Dark matter particle discovered?

JR Minkel reports this week from the temporary home of high-energy physics:
The American Physical Society meeting in St. Louis

April 14th, 2008
By JR Minkel

Researchers from Italy stirred up controversy eight years ago when they announced they had discovered the identity of dark matter, the invisible stuff that's thought to make up 23 percent of the universe. Now, after a long period of silence, the DAMA (DArk MAtter) collaboration at the University of Rome is about to reinforce its claim with fresh data. That's the rumor at the American Physical Society meeting here in St. Louis, anyway.

That's really all the information there is right now. The first data from the DAMA/LIBRA (Large sodium Iodide Bulk for RAre) experiment, an underground particle detector at the Gran Sasso National Laboratory in Italy, is indeed slated for announcement on Tuesday at the NO-VE International Workshop in Venice. I've put in some e-mails to try to find out more. Researchers haven't seen the new results, but they say it would take a lot to convince them that the DAMA team is really onto something.

Solving the dark matter mystery would of course be enormous news. Researchers have known since the 1930s that galaxies are spinning too fast at their outer edges to be made entirely of the kind of matter that we can see with our eyes. They believe that the visible stars and gas making up galaxies must be embedded in some kind of invisible or "dark" matter that provides added traction.

The identity of the dark matter is the big unknown. It has to be some entity that only rarely notices the presence of regular matter, and it can't be any of the known particles or else we would have detected it already. Researchers call these mystery widgets WIMPs, for weakly interacting massive particles. One potential source of WIMPs is a hypothetical add-on to the standard model of particle physics called supersymmetry, which for every known particle, conjures up a heavier counterpart.

In 2000 the DAMA group reported that it had found a small seasonal uptick in the number of particles smacking into sodium iodide detectors, after looking at three years' worth of data. They attributed the fluctuation to passing neutralinos, supersymmetry's counterpart to neutrinos, each one about 50 times the size of a proton.

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