Scientists closer to understanding dark matter

The Queen’s-affiliated SNOLAB is about to inherit one of the world’s most exciting research projects when it comes to understanding dark matter and the nature of the universe.

SuperCDMS – the next phase of the international Cryogenic Dark Matter Search (CDMS) experiment, currently located at the Soudan Underground Laboratory in Minnesota – plans to move to the world’s deepest large underground laboratory near Sudbury, ON.

“One of the most compelling problems of modern cosmology is that we don’t know what it is that makes up most of the matter in the universe,” says Queen’s physicist Wolfgang Rau, the only Canadian researcher on the current CDMS experiment.

CDMS has recently come closest to detecting the interaction of dark matter particles with ordinary matter. However, the search may be hampered by cosmic radiation, which can produce similar signals in the germanium (crystalline semi-conductor) detectors and make distinction difficult if there are too many of them. Being two kilometers underground, SNOLAB is more than twice as deep as the lab in Soudan, providing a much more efficient filter against this radiation.

Moreover SNOLAB is the only large underground laboratory in the world which will be run as a whole ‘clean lab’, filtering all dust from the air that would also be a source of interfering radiation.

Scientists believe that weakly interacting massive particles (WIMPs) could be the building blocks of dark matter, which constitutes 85 per cent of all matter in the universe. Passing through us at billions per second WIMPs are not usually perceptible since they seldom interact with normal matter.

Theory suggests these interactions occur as rarely as a few times per year in a five kilogram germanium detector. If however a WIMP does collide with an atomic nucleus in one of the germanium crystals, it puts the crystal into vibration like a little hammer ringing a bell.

“No WIMP has rung the bell yet but our results demonstrate the impressive potential of this technology and brings us one step closer to solving the dark matter mystery”, says Dr. Rau.

Determined to put more bells out there for the WIMPs to ring, the CDMS team plans to increase the detector mass from its current five kilograms to 25 kilograms in the SNOLAB phase of the experiment, at the same time improving the technology to take best advantage of the increased mass.

For more information please contact Communications Assistants Molly Kehoe, 613 533-2877, molly.kehoe@queensu.ca or Alissa Clark, 613 533-6000, ext. 77513, alissa.clark@queensu.ca, Queen’s News and Media Services.