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From News at Nature - Most Recent:
Rumours are swirling that a European satellite mission may have detected dark matter, the mysterious particles thought to make up as much of 85% of all matter in the Universe.
Nature has learned that the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) mission — a collaboration between Italy, Russia, Germany and Sweden — has detected a surplus of high-energy antielectrons whizzing through space. The antielectrons, also called positrons, could be the clearest signature yet of the dark matter lurking in the Milky Way, according to Dan Hooper, a theoretical physicist at Fermilab in Batavia, Illinois. "If it's true, it's a major discovery," he says.
Previous space and balloon missions saw hints of the same positron surplus in the 1990s. But their energy range was limited and their measurements had high uncertainty. PAMELA is, in principle, capable of detecting higher-energy positrons with far better accuracy than any other mission to date.
PAMELA's principal investigator, Piergiorgio Picozza, a physicist at the University of Rome Tor Vergata, declined to comment on the findings until they have been published. However, those who have seen the PAMELA data think they are telling. "This is the type of signal that one would expect [from dark matter]," says Graciela Gelmini, a theoretical physicist at the University of California, Los Angeles, who has studied the team's results. But Gelmini adds, the measurement is tricky, "so one has to be cautious".
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