Boffins shine new light on dark matter

Giant magnet in space shows 'existence of new physical phenomena'

Three-dimensional distribution of dark matter in the Universe

The LHC may have found the Higgs Boson, but overarching theories of everything have another hole: the observable universe weighs rather less than it ought if all those equations – and all the galaxies - are to hang together.

The inconvenient absence of so much matter gave rise to a theory that all the energy and matter needed to explain our explanation of the universe is out there, but is “dark” inasmuch as “it does not absorb, reflect, or emit light”, as CERN usefully explains.

Boffins now think they've found signs of dark matter's existence, but not the stuff itself, after experiments on the International Space Station, where a tool called the Alpha Magnetic Spectrometer (AMS, basically a colossal rare earth magnet in space ) was pressed in to service.

The AMS has been looking at cosmic rays of late, with the AMS' orbital position ideal for such observations because the rays are yet to be sullied by Earth's atmosphere. The results, CERN says, show rather more positrons than expected and “... are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations.”

CERN, which operates the AMS, is being very guarded about the new observations, saying through spokesboffin Professor Samuel Ting that “AMS is the first experiment to measure to 1% accuracy in space. It is this level of precision that will allow us to tell whether our current positron observation has a Dark Matter or pulsar origin.”

A paper reporting the observations from the AMS can be found here. A more-accessible, both in terms of language and paywalls, commentary in Physics offers this explanation for the results:

“The features in the AMS’s positron distribution are a striking confirmation—with unprecedented statistical detail—of what has been reported previously by satellite experiments: an excess of positrons over what we expect from known galactic energetic phenomena. There is a tantalizing—and much touted—possibility that this excess could be a signature of dark matter, though it’s much too soon to rule out more prosaic explanations.”

Not a sighting, then, but a clue that could lead to an understanding of what dark matter's fingerprints look like. That may sound less-than-thrilling, but the paper says the AMS readings “show the existence of new physical phenomena.” ®

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