The LUX-ZEPLIN (LZ) experiment, the world's most sensitive dark matter detector, has recorded a particle interaction that researchers cannot explain through known background signals involving ordinary matter. The event was found in data gathered over 220 live days between March 2023 and April 2024 at the Sanford Underground Research Facility in South Dakota.
LZ operates nearly a mile underground and uses seven tonnes of liquid xenon to search for weakly interacting massive particles, known as WIMPs. These hypothetical particles are a leading candidate for dark matter, which is estimated to make up approximately 85 percent of the universe's matter.
The event had a nuclear recoil energy of roughly 248 keV and appeared in an energy region where dark matter signals are expected and competing background noise is very low. The analysis covered 2.84 tonne-years of exposure. It was presented at the 2026 TeV Particle Astrophysics conference in Japan, and a paper has been submitted to Physical Review Letters and posted on arXiv.
The result has a statistical significance of 2.6 sigma. The researchers estimate there is a roughly 0.5% chance that known background interactions could explain the event. That remains below the 5-sigma threshold required for a definitive discovery, and the collaboration has cautioned that one event cannot confirm the detection of a dark-matter particle.
Rick Gaitskell, a professor at Brown University and LZ's spokesperson, said the event was intriguing and had appeared in the region where dark matter is expected with very low competing backgrounds. An international collaboration of 250 scientists and engineers from 39 institutions operates the experiment.
If dark matter caused the interaction, the particle would likely be a WIMP with a mass of at least 200 gigaelectronvolts, or more than 200 times the mass of a proton. That would point towards a heavier type of WIMP than many researchers had originally expected. Earlier LZ analyses focused on lower-energy interactions, while this study widened the search to higher-energy signals.
More data and outside scrutiny will determine whether the signal holds up. Detectors including XENON in Italy and PandaX in China could help check the result over the coming months. Decades of searches have yet to produce a confirmed direct detection of a dark-matter particle candidate.
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