Hunting for dark matter in a gold mine

"What really impressed me was the trip down," said astrophysicist James Buckley, PhD, speaking of the vertical mile he traveled to get to the site of an underground dark-matter experiment. "You can see you're moving at a pretty good clip, which, by the way, is three times slower than the cage used to drop when it was a mine. It took us 10 minutes to get down a mile. You just watch the earth flashing by and every once in a while you go past a boarded up tunnel."

The mine is the Homestake Mine, a played-out gold mine in Lead, S.D., that has been converted into a warren of underground chambers housing physics experiments that need to be shielded from cosmic radiation.

One of these experiments is the Lux detector, designed to detect WIMPs (weakly interacting massive particles). WIMPs are hypothetical subatomic particles thought to make up dark matter in much the same way that electrons and quarks make up ordinary matter. But compared to other particles, WIMPs are elusive and interact only rarely with ordinary matter, and so far Lux hasn't found any.

Buckley, a professor of physics in Arts & Sciences at Washington University in St. Louis, is a co-investigator on a team building a supersized version of Lux, called Lux-Zeplin, that will be roughly 100 times more sensitive to dark matter than its predecessor. Lux-Zeplin and two other dark-matter experiments survived a stringent "downselection" of competing dark-matter experiments and received Department of Energy and the National Science Foundation funding this July.