A mile underground, physicists caught the universe's first dark matter hint

An underground detector in South Dakota has recorded a single strange event that may have been triggered by a dark matter particle, the substance thought to make up roughly 85 percent of the universe's matter but never directly seen. Sam Eriksen, a particle physicist at the University of Bristol, said the finding "could be the first hint of a dark matter observation." He and colleagues announced the result on September 1 at a conference in Japan and posted a preprint online. The detector, part of the LUX-ZEPLIN experiment, sits nearly a mile underground in a tank of liquid xenon. Combing 220 days of data, the team found one high-energy interaction hard to explain with ordinary matter. It is not a discovery. Statistical analysis puts the odds of a mundane explanation at about 0.5 percent, short of the threshold physicists require. Nobody is claiming victory. "It's only one event," said Dan Hooper, a physicist at the University of Wisconsin-Madison. "So who knows what's really going on here."