Massive dark matter experiment receives funding

A member of the Large Underground Xenon collaboration inspects their dark matter detector before turning it on for a previous trial run. The LUX detector is the most sensitive dark matter detector in the world and will be replaced by the much larger, more sensitive LUX-ZEPLIN experiment. Photo courtesy of Matt Kapust/Sanford Lab

LEAD — The U.S. Department of Energy (DOE) and the National Science Foundation (NSF) announced Friday that they’ve chosen to support three second generation dark matter experiments, including the Sanford Underground Research Facility’s LUX-ZEPLIN, or LZ dark matter experiment, which will eventually replace the Large Underground Xenon (LUX) dark matter experiment at the Lab’s Davis Campus, one mile below the city of Lead.

“This is great news for the future of dark matter exploration and the Sanford Lab,” said Mike Headley, executive director of the South Dakota Science and Technology Authority. “The LZ experiment will play a key role in the future of the lab and we’re pleased that the DOE selected the experiment. It certainly will extend the state’s investment in this world-class facility.”

Second generation dark matter experiments are those at least 10 times more sensitive than currently operational dark matter experiments. LZ, which has been in the planning stage for several years, is expected to be roughly 1,000 times more sensitive than LUX, which was crowned the most sensitive dark matter experiment in the world in October after its initial three month run.

LZ, like LUX, will search for weakly interacting massive particles, or WIMPs, which rarely interact with ordinary matter except through gravity.

LUX is a 6-foot-tall, enclosed titanium bucket filled with 800 pounds of liquid xenon inside a two-story water tank filled with 70,000 gallons of ultra-pure water, buried 4,850 feet underground. LZ will be a much bigger bucket inside the same tank — 15,430 pounds of liquid xenon instead of 800.

But how exactly do these two generations of dark matter detectors go about hunting down evidence of dark matter? It’s all in the xenon.

If a WIMP collides with a xenon atom the two will bounce off one another, the xenon atom emitting a slight electric charge and a flash of light. An array of highly-sensitive detectors inside LUX’s central tank are primed and ready to capture just these kinds of events. And when they occur, LUX can measure the energy of the event with unparalleled precision. LZ, of course, will contain even more detectors, thus increasing the chance of catching such an occurrence with precision and certainty.

“We’re elated and excited,” said Harry Nelson, spokesman for the LZ collaboration. “In my career — and I’m getting old now — LZ is right up there with the best, and I’ve been in eight or 10 projects like this, now. I’m really happy to be part of it.”

The search for dark matter is the search to understand roughly 27 percent of the universe that we know nothing about with any certainty — that’s how much of the total cosmos scientists theorize is dark matter. Dark energy likely accounts for another 68 percent of the invisible cosmos.

“This is one of the biggest mysteries of the universe. Sometimes, I think, we feel like we know all this stuff. In the 370-some years of science since Galileo’s death, we think we’ve discovered so many things in those years, but we still don’t know what something like 95 percent of the matter of universe even is,” said Nelson. “People want to portray themselves as experts, and we only know 5 percent of what’s out there at the most. I love that. The thought that we’re going to figure out what the rest of this stuff is really, really exciting.”

Kevin Lesko, Sanford’s lead scientific investigator and physicist with the Lawrence Berkeley National Laboratory in Berkeley, California said the plan is to have LZ operational by 2018. In the meantime LUX will continue searching for dark matter.

Both LUX and LZ include more than 100 collaborators from universities around the world, including two from in state: South Dakota School of Mines and Technology and the University of South Dakota.

The DOE and NSF agencies also announced plans to support the Super Cryogenic Dark Matter Search at SNOLAB in Ontario, Canada, and the second generation Axion Dark Matter Experiment, or ADMX-Gen2, at the University of Washington, Seattle.

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