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OSB archive

Halos may help us 'see' dark matter

Pete Wilton

New calculations suggest that the halos caused when dark matter particles collide could be frequent enough to help us detect them within a year.

The team, including Joseph Silk of Oxford University's Department of Physics, detailed their findings in a recent Science Express paper reported by PhysOrg.com.

Previous studies had suggested that such quantum collisions - termed annihilations - would be few and far between, and so the gamma rays they emit would be hard to pick up even by orbiting satellite telescopes such as NASA's Fermi.

But the team's analysis of data from previous observations picked up more collisions than expected. They theorised that this might be down to an attractive force, the Sommerfeld effect, pulling dark matter particles more closely together and so making collisions more likely.

By applying these new calculations to a model of a dark matter cloud the size of our Milky Way the researchers were able to predict that Fermi should be able to detect a few subhalos caused by these collisions in its first year of operation, and find at least ten after five years.

Such observations would give the first direct evidence for the existence of dark matter - something that would rate as one of the all-time great physics discoveries.

The work was carried out by Michael Kuhlen of the Institute for Advanced Study in Princeton, Piero Madau of the University of California, Santa Cruz, and Joseph Silk of the University of Oxford.