VERMILLION, S.D. – The University of South Dakota will play a key role in the international collaboration SuperCDMS SNOLAB experiment which will begin operations in the early 2020s to hunt for hypothetical dark matter particles called weakly interacting massive particles, or WIMPs.
“Constructing the SuperCDMS experiment at SNOLAB is an endeavor that requires close collaboration between a large number of scientific groups,” said Joel Sander, an assistant professor of physics. “The collaboration enables SuperCDMS to use a wide range of expertise to build a successful experiment.”
Sander’s group at USD plays a central role building the data quality system and leads the detector configuration development. The experiment will be at least 50 times more sensitive than its predecessor, exploring WIMP properties that can’t be probed by other experiments and giving researchers a powerful new tool to understand one of the biggest mysteries of modern physics.
“In addition to USD, a number of U.S. and Canadian universities as well as three U.S. national labs – the Fermi National Laboratory, Pacific Northwest National Laboratory, and SLAC National Accelerator Laboratory – are heavily involved with the experiment, ranging from detector fabrication and testing to data analysis and simulation,” said Sander. “The largest international contribution comes from Canada and includes the research infrastructure at SNOLAB where the experiment will take place."
The experiment will be assembled and operated at the Canadian laboratory SNOLAB– 6,800 feet underground inside a nickel mine near the city of Sudbury. It’s the deepest underground laboratory in North America. There it will be protected from high-energy particles, called cosmic radiation, which can create unwanted background signals that interfere with the search for WIMPs.
Scientists know that visible matter in the universe accounts for only 15 percent of all matter. The rest is a mysterious substance, called dark matter. Due to its gravitational pull on regular matter, dark matter is a key driver for the evolution of the universe, affecting the formation of galaxies like our Milky Way. It therefore is fundamental to our very own existence.
But scientists have yet to find out what dark matter is made of. They believe it could be composed of dark matter particles, and WIMPs are top contenders. If these particles exist, they would barely interact with their environment and fly right through regular matter. However, every so often, they could collide with an atom of our visible world, and dark matter researchers are looking for these rare interactions.
In the SuperCDMS SNOLAB experiment, the search will be done using silicon and germanium crystals, in which the collisions would trigger tiny vibrations. However, to measure the atomic jiggles, the crystals need to be cooled to less than minus 459.6 degrees Fahrenheit – a fraction of a degree above absolute zero temperature. These ultracold conditions give the experiment its name: Cryogenic Dark Matter Search, or CDMS. The prefix “Super” indicates an increased sensitivity compared to previous versions of the experiment.
The collisions would also produce pairs of electrons and electron deficiencies that move through the crystals, triggering additional atomic vibrations that amplify the signal from the dark matter collision. The experiment will be able to measure these “fingerprints” left by dark matter with sophisticated superconducting electronics.
"Understanding the nature of the dark matter is one of the biggest questions of our age,” said Sander. “We are excited to get to work.”