Physicists try to make sense of a dark matter puzzle from space
By Tom Miles GENEVA (Reuters) - A minibus-sized box of sensors whizzing round the earth every 91 minutes has sent back data that is tantalising theorists who want to know why their existing model of the universe no longer adds up. Clamped to the International Space Station, the 7.5-tonne Alpha Magnetic Spectrometer (AMS) intercepts particles from outer space, looking for evidence of "dark matter", which has never been seen but is thought to be five times as abundant in the universe as visible matter. "AMS is a camera taking pictures of cosmic rays. We are taking 1,000 pictures per second," said Stefan Schael, a professor at RWTH Aachen University. The space camera gives a new perspective on results gathered on earth at the CERN physics research centre's Large Hadron Collider (LHC) near Geneva. The sets of data from the camera and the LHC don't match. "At the LHC we have found exactly what we were predicting. At AMS we found only things that we were not expecting," said Schael. "The problem is that in the LHC data there is no room for something new." Compared to the LHC, AMS found too many anti-particles such as positrons and anti-protons coming from space, which might be the "fingerprints" of dark matter, Schael told Reuters at CERN, where leading theoretical physicists compared notes during a three-day meeting this week. "We have invited experts from all over the world, looking at this data and confronting it with their theories. None of them is able to describe with accuracy what we observe. Which means all of the various approaches are missing something." Samuel Ting, the 79-year-old Nobel laureate who leads the AMS experiment and who persuaded the U.S. Congress to send it up on the Space Shuttle in 2011, appeared to be enjoying the scramble caused by the findings. "So far so good, so far so good," he said. "There are many many explanations. Some people think it's dark matter, there are 350 papers on that. Some people said no, it's a new acceleration mechanism. Some people think it's a supernova remnant ... Eventually with the help of theorists we will gradually close the gap." The LHC may yet provide answers, since it is being restarted after a two-year shutdown at twice the energy level that enabled CERN to confirm the existence of the elusive Higgs Boson particle two years ago. CERN's Director General Rolf Heuer said finding the Higgs was just "a good warm-up" compared to the potentially open-ended search for dark matter. (Editing by Andrew Roche)
