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Exciting new light on a mysterious shadow universe

New York: A concatenation of puzzling results from an alphabet soup of satellites and experiments has led a growing number of astronomers and physicists to suspect that they are getting signals from a shadow universe of dark matter that makes up a quarter of creation but has eluded direct detection until now. Maybe.

“Nobody really knows what’s going on,” said Gordon Kane, a theorist at the University of Michigan. Physicists caution that there could still be a relatively simple astronomical explanation for the recent observations.

But the nature of this dark matter is one of the burning issues of science. Identifying it would point the way to a deeper understanding of the laws of nature and the Einsteinian dream of a unified theory of physics.

The last few weeks have seen a blizzard of papers trying to explain the observations in terms of things like “minimal dark matter” or “exciting dark matter,” or “hidden valley” theory, and to suggest how to look for them in particle accelerators like the Large Hadron Collider, set to begin operation again outside Geneva next year.

“It could be deliriously exciting, an incredibly cool story,” said Nima Arkani-Hamed of the Institute for Advanced Study in Princeton, who has been churning out papers with his colleagues. “Anomalies in the sky tell you what to look for in the collider.”

On Thursday, a team of astrophysicists working on one of the experiments reported in Nature that a cosmic ray detector onboard a balloon flying around the South Pole had recorded an excess number of high-energy electrons and their antimatter opposites, positrons, sailing through local space.

The particles, they conceded, could have been created by a previously undiscovered pulsar, the magnetised spinning remnant of a supernova explosion, blasting nearby space with electric and magnetic fields. But, they say, a better and more enticing explanation for the excess is that the particles are being spit out of the fireballs created by dark matter particles colliding and annihilating one another in space.

“We cannot disprove that the signal could come from an astrophysical object. We also cannot eliminate a dark matter annihilation explanation based on current data,” said John P. Wefel of Louisiana State University, who leads the team. “Whichever way it goes, for us it is exciting.”

The results came on the heels of a report earlier this year from Pamela, a satellite built by Italian, German, Russian and Swedish scientists to study cosmic rays. Pamela scientists reported, had recorded an excess of high-energy positrons. This, they said, “may constitute the first indirect evidence of dark matter particle annihilations,” or a nearby pulsar. — New York Times News Service

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