PAMELA reasserts positron excess

Published in Physics World, 23 Aug 2013

The European collaboration PAMELA has published new data concerning a mysterious excess of positrons that permeate outer space. The data, which describe the collaboration’s first detection of absolute rather than relative positron numbers, could help refine theoretical models – including those that explain the excess as a footprint of dark matter.

PAMELA (Payload for Antimatter/Matter Exploration and Light-nuclei Astrophysics) is a satellite that was launched in 2006 by institutions in Germany, Italy, Russia and Sweden to examine the nature of antiparticles in cosmic rays. The first results, published in 2008, revealed a surprising feature: a steady rise in the ratio of positrons to electrons above an energy of about 10 GeV. This is contrary to basic theoretical calculations, which predict that the positron fraction should have decreased. […]

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