Dark matter detector nears activation

• LUX experiment

In this Oct. 16 photograph provided by Sanford Lab University of California, Davis, physicist Jeremy Mock inspects the Large Underground Xenon experiment detector, cylinder at center, that has now been lowered into its 70,000-gallon home in a water tank a mile beneath the earth’s surface in a shuttered gold mine in Lead. (AP file photo)

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Scientists hoping to detect dark matter deep in a former South Dakota gold mine have taken the last major step before flipping the switch on their delicate experiment and say they may be ready to begin collecting data as early as February.

What’s regarded as the world’s most sensitive dark matter detector was lowered earlier this month into a 70,000-gallon water tank nearly a mile beneath the earth’s surface, shrouding it in enough insulation to hopefully isolate dark matter from the cosmic radiation that makes it impossible to detect above ground.

And if all goes as planned, the data that begins flowing could answer age-old questions about the universe and its origins, scientists said Monday.

“We might well uncover something fantastic,” said Harry Nelson, a professor of physics at University of California, Santa Barbara and a principal investigator on the Large Underground Xenon experiment. “One thing about our field is that it’s kind of brutal in that we know it’s expensive and we work hard to only do experiments that are really important.”

This one hasn’t been cheap, at about $10 million, but like the discovery of the Higgs boson — dubbed the “God particle” by some — earlier this year in Switzerland, the detection of dark matter would be a seismic occurrence in the scientific community.

Scientists know dark matter exists by its gravitational pull but, unlike regular matter and antimatter, it’s so far been undetectable. Regular matter accounts for about 4 percent of the universe’s mass, and dark matter makes up about 25 percent. The rest is dark energy, which is also a mystery.

The search in South Dakota began in 2003 after the Homestake Gold Mine in the Black Hills’ town of Lead, shuttered for good. Scientists called dibs on the site, and in July, after years of fundraising and planning, the LUX detector moved into the Sanford Underground Research Facility, 4,850 feet below the earth’s surface. It took two days to ease the phone booth-sized detector down the once-filthy shaft and walkways.

There, the device was further insulated from cosmic radiation by being submerged in water that’s run through reverse osmosis filters to deionize and clean it.

“The construction phase is winding down, and now we’re starting ... to operate the systems underground,” said Jeremy Mock, a graduate student at the University of California, Davis who has worked on the LUX experiment for five years.

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