Large Underground Xenon detector
M. Kapust/Sanford Underground Research Facility

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Dark matter search comes up empty

The latest, most sensitive search for particles of dark matter—the bizarre invisible stuff in which our galaxy appears to be embedded—has come up empty. Since 2012, physicists working with the Large Underground Xenon (LUX) detector, pictured above, had been searching for evidence of so-called weakly interacting massive particles, or WIMPs, bumping into the atomic nuclei in 370 kilograms of frigid liquid xenon. But the experiment, which is housed 1480 meters deep in the Sanford Underground Research Facility in Lead, South Dakota, ended its final 20-month run in May, and researchers see no evidence for such particles, as they reported today at a conference in Sheffield, U.K. Physicists will continue to search for WIMPs—their candidate for the dark matter whose gravity appears to bind the galaxies. Experimenters working in Italy’s subterranean Gran Sasso National Laboratory in L'Aquila are firing up XENON1T, a detector that contains 3.5 metric tons of liquid xenon, which should be 100 times more sensitive than LUX. And LUX researchers are working on an upgraded detector called LZ, which would contain 10 metric tons and come on in 2020. Meanwhile, physicists’ enthusiasm for WIMPs may be cooling—not just because they haven’t found them yet, but also because experimenters working with the world’s biggest atom smasher, Europe’s Large Hadron Collider, have yet to blast such particles into existence, as theory suggests it should.