Dark-matter detector has new home in South Dakota

By AMBER HUNT
Associated Press

LEAD, S.D. (AP) — After a painstakingly slow two-day move from the earth's surface, the world's most sensitive dark-matter detector has a new home nearly a mile underground in a shuttered South Dakota gold mine.

And when the switch is flipped later this year to start collecting data, scientists say it could be a Higgs boson-style celebration all over again.

"Dark matter presents a much bigger problem to detect and is more speculative than the Higgs," said Tom Shutt, a physics professor with Case Western Reserve University who's working on the Large Underground Xenon detector, known as LUX.

"If we find it, it's going to be a much bigger shift in our understanding of physics."

A breakdown for laymen: The Higgs boson is a subatomic particle that scientists believe gives other particles mass. Scientists earlier this month announced a breakthrough in the existence of Higgs boson, sometimes called the "God particle" because its existence is key to understanding the early evolution of the universe.

Dark matter, meanwhile, is elusive matter that scientists believe makes up about 25 percent of the universe. They know it's there by its gravitational pull, but unlike regular matter and antimatter, it's so far undetectable.

Regular matter, such as people and planets, make up about 4 percent of the total-mass energy of the universe. By discovering dark matter, scientists could explain why the universe isn't made up equally of matter and antimatter. That, in turn, could explain how the world as we know it came to be.

The Sanford Underground Research Facility was unveiled in May 4,850 feet beneath the earth within the closed Homestake Gold Mine in Lead, a town nestled in South Dakota's Black Hills. The mine opened in 1876 during the area's gold rush but shuttered in 2003 after a slow decline in the value of gold.

The mine is useful for this project because dark matter is too sensitive to detect in normal laboratories. By setting up LUX nearly a mile underground — and then submerging it in liquid cooled to -100 degrees centigrade — it should be shielded from pesky cosmic radiation that interferes with detection.

"It was a bit of a nail-biter," Yale Physics Professor Dan McKinsey said of the detector's trip underground. "We always worry there might be something you didn't think of that could go wrong."

The move was meticulous: First, the 6,000-pound experiment was taken from its temporary home in a surface-level lab and carefully inched toward a shaft previously used by miners. The ride down the shaft usually takes 15 minutes; for the detector, the trip was slowed to two hours.

Wrapped in protective foam and plastic, it then was moved 500 feet to its final home on air bearings to protect it from even the slightest jiggle.

Now that the LUX is in the Davis Cavern — named after Nobel Prize winner Ray Davis — it can be submerged in a water shield and connected to support systems that could begin collecting data as early as December.

If that data uncovers dark matter as hoped, expect to see scientists pouring more champagne.

"These are two huge mysteries that will have opened up in the last 30 years," Shutt said. "We're all going after the same thing: We're trying to figure out what are the basic components of the universe."