PAMELA MAY HAVE SPOTTED THE DARK STUFF
By Ron CowenWeb edition : Thursday, September 4th, 2008   

Data from an orbiting observatory record more positrons than standard model accounts forCosmologists are agog about the possibility that an orbiting observatory may have discovered particles of dark matter — the proposed, invisible material that researchers believe makes up most of the mass of the universe.

At two meetings in August, researchers analyzing data from the Russian-European observatory PAMELA, short for Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics, reported preliminary evidence that the device had recorded more positrons from the Milky Way than could be accounted for by the standard model of elementary particle physics.

At the International Conference on High Energy Physics, held in Philadelphia, PAMELA researcher Mirko Boezio of the Italian National Institute of Nuclear Physics in Trieste suggested that the surplus of positrons — the electron's antiparticle, which is equal in mass but opposite in charge — could be accounted for by the annihilation of pairs of dark-matter particles. According to an existing theory, when dark-matter particles collide, they decay into a spray of ordinary, visible particles, including an abundance of positrons.

"We plan to have final results ready by early October and submit a paper to a peer-reviewed journal," Boezio told Science News. Until then, he says, the findings remain preliminary, and "We prefer to withhold further comments."

But that hasn't stopped other researchers from posting their interpretations of the data on the Internet.