LUX Detector Narrows Search for Dark Matter

Dan McKinsey co-spokesperson for LUX

Thursday, July 21, 2016

A 20-month experiment to detect dark matter from the depths of an abandoned gold mine has come to an end, narrowing the search for, but failing to find, an elusive particle that should be everywhere.

The Large Underground Xenon dark matter experiment, or LUX, is operated beneath a mile of rock at the Sanford Underground Research Facility in the former Homestake gold mine in the Black Hills of South Dakota. It’s mission: to detect so-called weakly interactive massive particles, or WIMPS, that some physicists think comprise the mysterious dark matter that makes up 85 percent of all the matter in the universe.

If the WIMP hypothesis is correct, billions of these particles pass through our bodies every second, as well as Earth and everything on it. But because WIMPs interact so weakly with ordinary matter, this ghostly traverse goes entirely unnoticed.

Despite the LUX team’s non-discovery, they have narrowed the mass-range in which the putative particle can exist, focusing future searches within that range.

“The extra experiment gave us more sensitivity in searching for high-mass dark matter particles,” said Daniel McKinsey, a UC Berkeley professor of physics and senior faculty scientist at Lawrence Berkeley National Laboratory, and co-spokesperson for LUX. “Many theorists think that the dark matter mass will be high, around a thousand times the mass of a proton.”

Overall, the last 20-month experiment provided about four times better sensitivity to high-mass particles than earlier underground experiments that began in 2013.

LUX’s sensitivity far exceeded the original goals for the project, according to McKinsey, which makes the team confident that if dark matter particles had interacted with the LUX’s xenon target, the detector would almost certainly have seen it. That enables scientists to confidently eliminate many potential models for dark matter particles, offering critical guidance for the next generation of dark matter experiments.

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