In former gold mine, scientists lie in wait for dark matter

Oct 17, 2013 by Eric Gershon
In former gold mine, scientists lie in wait for dark matter
Scientists are hunting for dark matter deep underground in South Dakota. Here, Yale postdoctoral researcher Markus Horn works on the LUX collaboration's xenon gas system, part of an elaborate experiment to capture dark matter particles for the first time. Credit: C.H. Faham/Brown University

(Phys.org) —Nicole Larsen, a fifth-year graduate student at Yale, couldn't talk by phone. "I'm 4,850 feet below the surface," she said, by Skype, on a recent afternoon.

Over the summer Larsen, a particle physicist, spent most of her daylight hours at the bottom of an old gold mine in the Black Hills of South Dakota, 50 miles northwest of Mount Rushmore and a 30-minute drive from the nearest supermarket. She was helping to hunt for , a mysterious substance estimated to make up as much as 85% of the universe's total matter.

Scientists have inferred dark matter's existence, but never detected it directly. Teams of researchers around the world are racing to be the first, including Larsen's, a collaboration known as the Large Underground Xenon dark matter experiment, or LUX.

"Knowing more about dark matter will give us ideas about the future of our planet, galaxy, and universe," she said from the former Homestake gold mine, nearly a mile inside Earth. "This search has implications for how the universe got to be the way it is and for what's going to happen to us in the future as well."

About a dozen Yale researchers are now involved in LUX. The full collaboration involves more than 100 researchers from 17 institutions. Daniel McKinsey, an associate professor of physics at Yale and one of LUX's senior scientists, leads the Yale contingent and serves as the collaboration's co-spokesman. On Oct. 30 LUX plans to release its first results.

"Dark matter is one of the huge mysteries of modern science," McKinsey said. "Its effects are widespread in the universe. Knowing its properties would be revolutionary for particle physics."

Less than 15% of the universe is made up of conventional matter—protons, neutrons, electrons. Most of the rest is thought to be dark matter, which cannot be seen or felt, and seems to interact weakly, if at all, with conventional matter. (Hence the nickname for dark matter particles—WIMPs, or weakly interacting massive particles.) Identifying the raw material of the universe is a high priority for physicists and astronomers.

Scientists have inferred its existence from the behavior of known entities, such as galaxies. Conventional matter cannot explain the ability of galaxies to keep their form while rotating at current speeds, for example. Dark matter may provide the extra mass that would make this possible.

In a one-of-a-kind laboratory at the bottom of the Homestake mine, in Lead, S.D., the LUX scientists have designed and built a sophisticated device for taking dark matter's fingerprint. It's about the size of a telephone booth and called a liquid xenon detector.

Xenon is one of the noble (or rare) gases. Its high density in liquid form is useful for catching subatomic particles moving at high speeds, as dark matter is believed to be. A vat of liquid xenon equipped with arrays of ultra-sensitive light detectors sits in a tank of water. The researchers believe that dark matter particles, which can penetrate deep into the earth, will collide with xenon atoms and bounce off their nuclei, jarring the xenon and generating a fluorescence the detector has been designed to notice.

The layers of rock surrounding the lab are intended to help minimize interference by various particles that endlessly bombard earth's surface. These particles, such as high-energy neutrons and muons, would make it harder for scientists to discern the presence of dark matter particles—a difficult task as it is.

"It's like trying to spot a single snowflake in a blizzard or hear a single voice in Times Square," said McKinsey. "You're digging a signal out of a lot of noise."

And digging for something akin to physics gold: "Because the dark matter particle would be a 'new' particle," McKinsey said, "it would also be the first particle discovered outside of the Standard Model of particle physics," the prevailing theory that describes the fundamental particles of matter and how they interact.

McKinsey's group has played an important role in the collaboration, with primary responsibility for several of the detector's major components, including the all-important xenon gas circulation, purification, and recovery systems. "We need the xenon to be exceptionally pure—sub part-per-billion levels of impurity," he said recently. Much of the team's work has taken place in South Dakota, and nearly every member has worked in the 's lab, known as known as the Sanford Underground Research Facility, or at a surface lab nearby. Important projects have also been carried out in New Haven, where the team invented some essential technologies from scratch. McKinsey and his squad of postdocs, graduate students, and undergraduates shuttle back and forth between coastal Connecticut and South Dakota's Black Hills.

To reach the two-story subterranean lab at Lead, researchers ride an elevator they call "the cage." Wearing coveralls, hard hats, and steel-toe boots, they load into it at 7:15 a.m. for a prompt 7:30 departure. The ride takes about 10 minutes. When they exit at bottom, a glance to the left reveals a dark, muddy hole, an abandoned passageway for the gold miners of yesteryear. The scientists all go right, into a high-grade science lab flooded in fluorescent light.

"Once we detect dark matter, assuming we one day do, there's a gazillion other experiments we can do to understand it better," said McKinsey. "The key is seeing it first."

Explore further: Scientists crank up the voltage, create better dark-matter search

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vacuum-mechanics
1 / 5 (16) Oct 17, 2013
Scientists have inferred dark matter's existence, but never detected it directly. Teams of researchers around the world are racing to be the first, including Larsen's, a collaboration known as the Large Underground Xenon dark matter experiment, or LUX.
"Knowing more about dark matter will give us ideas about the future of our planet, galaxy, and universe," she said from the former Homestake gold mine, nearly a mile inside Earth….

It seems quite difficult to find the dark matter, while waiting; this simple physical view may give some idea ….
http://www.vacuum...14〈=en
GuruShabu
1.3 / 5 (14) Oct 17, 2013
Dark matter and dark energy do not exist.
This is a twisted result of poor science that has created an ad hoc theory to explain something that they could not explain.
Now they are squandering billions of dollars on "research" and I am sure they will never find it.
It is the same with AGW - Anthropogenic Global Warming.
The media helps the spread of an "idea" that after some time gets a momentum after being repeated so many millions of times. And abracadabra! Institutions, grants and most importantly, carriers are engaged on the "field" and it will take decades to realise that field is sterile.
Just have a look how many thousands of Post Doc research on "String Theory" just because it is mathematically beautiful!
The peer reviewers will make it sure the subject gets an extra push for quite a while and the wrong limb is stablished and it will grow regardless its nature.
Nanowill
1 / 5 (10) Oct 17, 2013
Dark matter probably does not exist. The flattening of galactic rotation curves is due to a quantum effect which is why it always occurs at the same very low gravitational field strength.
With that explained are there any other reasons to suppose CDM exists?

Dark energy does exist, i.e. the reason the Universe is expanding and seems to be being pulled outward, even while its density is decreasing. The explanation for this? Its an indirect result of quantized gravity. .
jt dwyer
1 / 5 (2) Oct 30, 2013
"Scientists have inferred its existence from the behavior of known entities, such as galaxies. Conventional matter cannot explain the ability of galaxies to keep their form while rotating at current speeds, for example. Dark matter may provide the extra mass that would make this possible."

IMO, it was primarily the discrepancy between observations and the results of improperly applied Keplerian dynamics that was used to infer the existence of galactic dark matter. If there was no perceived requirement for rotational velocities of objects within the planar disks of spiral galaxies to diminish as a function of radial distance in vast, self-gravitating compound disk structures, there would be little need for the compensatory mass of enormous dark matter halos...
yyz
3 / 5 (2) Oct 30, 2013
"If there was no perceived requirement for rotational velocities of objects within the planar disks of spiral galaxies to diminish as a function of radial distance in vast, self-gravitating compound disk structures, there would be little need for the compensatory mass of enormous dark matter halos..."

Dark matter halos in galaxies are also inferred by observations of galaxy-galaxy lensing:

http://arxiv.org/.../0606447

http://arxiv.org/abs/1003.5567
jt dwyer
not rated yet Oct 30, 2013
xyz,
I'm having difficulty posting a more proper response, but your references refer to elliptical galaxies. The second one is the more useful. Spiral galaxies typically only produce strong lenses when bulge dominated spiral galaxies are viewed edge-on - presenting an elliptical focus. See arxiv 1303.6896
yyz
5 / 5 (1) Oct 30, 2013
"Spiral galaxies typically only produce strong lenses when bulge dominated spiral galaxies are viewed edge-on"

Not necessarily (e.g.: http://iopscience...ulltext/ ). But regardless, spiral and elliptical galaxies both require dark matter to explain strong lensing observations, per my previous links and:

http://ned.ipac.c...er5.html

http://dspace.mit...0751.pdf

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