The world’s largest dark matter detector, LUX-ZEPLIN (LZ), has recorded a single unusual particle event, announced at the TeV Particle Astrophysics conference in Japan. Physicists caution it is too early to claim a discovery, but the signal could hint at dark matter. Tom Shutt of SLAC National Accelerator Laboratory and co-founder of LZ said the team decided to publish and scrutinize the event deeply.

Wick Haxton of UC Berkeley likened the find to seeing a present under the Christmas tree—exciting regardless of outcome. The LZ detector, containing 7 tons of frigid liquid xenon, operates 1480 meters deep in the Sanford Underground Research Facility in South Dakota. It has searched for weakly interacting massive particles (WIMPs) since 2021 without success until now.

The event showed a nuclear recoil of 248 keV, far higher than expected for ordinary WIMPs. Rick Gaitskell of Brown University, LZ spokesperson, noted such high-energy recoils would require thousands of lower-energy events if from standard WIMPs—none have been seen. The team will submit findings to Physical Review Letters and explore more complex models to explain the anomaly.