Record-Setting Dark Matter Detector Comes Up Empty -- and That's Good News

An anonymous reader quotes a report from Gizmodo: WIMPs (weakly interacting massive particles) are one of the most serious contenders for dark matter -- the 'missing' mass supposedly constituting 85% of our universe. Given its elusiveness, dark matter tests the patience and creativity of physicists. But the latest results from LUX-ZEPLIN (LZ), the South Dakota-based detector, may have brought scientists a small step closer to catching WIMPs in action. In a recent Physical Review Letters paper, scientists analyzed 280 days' worth of data from LUX-ZEPLIN, reporting the tightest ever upper limit on the interaction strength of WIMPs. The result -- a near fivefold improvement -- demonstrates how physicists are increasingly getting better at circumventing the problem that dark matter is, well, dark; the elusive stuff evades any detection method that depends on materials interacting with visible light or other types of radiation.

The LUX-ZEPLIN experiment, located one mile underground in a decommissioned South Dakota gold mine, employs nearly 15,000 pounds (7 tons) of liquid xenon. The chemical element's high atomic mass and density make it potentially easier for scientists to detect any unknown particles that may pass through the detector. Also, liquid xenon is transparent, preventing any unwanted noise -- usually arising from radioactive matter around the detector -- from spoiling an experiment. 'These results firmly establish that LZ is the world's most sensitive search for dark matter heavier than 10 GeV, that's about 10 times heavier than a proton,' explained Scott Haselschwart, a physicist at the University of Michigan and LZ physics coordinator, in an email to Gizmodo. 'To put our result in perspective: we have ruled out dark matter that would interact only once in a single kilogram of xenon every four millennia!' 'LZ is the most sensitive search for WIMP dark matter to date, but we still have another two years of data to collect,' Haselschwart said. 'This means that a discovery of dark matter in LZ could come anytime now. We are truly looking for dark matter where no one has ever looked before and that is extremely exciting!'

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