Next-generation dark matter experiments get the green light

July 16, 2014 by Kate Greene, Lawrence Berkeley National Laboratory

The LZ water shield, currently housing the LUX experiment.
( —Last week, the U.S. Department of Energy's Office of Science and the National Science Foundation announced support for a suite of upcoming experiments to search for dark matter that will be many times more sensitive than those currently deployed.

These so-called Generation 2 Dark Matter Experiments include the LUX-Zeplin (LZ) experiment, an international collaboration formed in 2012, managed by DOE's Lawrence Berkeley National Lab (Berkeley Lab) and to be located at the Sanford Underground Research Facility (SURF) in South Dakota. With the announcement, the DOE and NSF officially endorsed LZ and two other experiments.

"The great news is we've been given the go-ahead," says William Edwards, LZ project manager and engineer in Berkeley Lab Physics Division. "We're looking forward to making what has been a proposal into a real, operational, first-rate experiment."

The LZ experiment was first proposed two years ago to search for and advance our understanding of dark matter, a mysterious substance that makes up roughly 27 percent of the universe. The experiment will build on the current dark matter experiment at SURF called the Large Underground Xenon detector, or LUX.

Dark matter, so named because it doesn't emit or absorb light, leaves clues about its presence via gravity: it affects the orbital velocities of galaxies in clusters and distorts light emitted from background objects in a phenomenon known as gravitational lensing. But direct detection of dark matter has so far been elusive.

3D rendering of the LZ detector.

Physicists believe dark matter could be made of difficult-to-detect particles called Weakly Interacting Massive Particles or WIMPs, which usually pass through ordinary matter without leaving a trace. The current LUX experiment consists of a one-third ton liquid xenon detector that sits deep underground where it is shielded from cosmic rays and poised to find WIMPs. When one of these particles passes through the xenon detector, it should occasionally produce an observable flash of light.

"When completed, the LZ experiment will be the world's most sensitive experiment for WIMPs over a large range of WIMP masses," says Harry Nelson, physicist at the University of California, Santa Barbara and current spokesperson of the LZ Collaboration. The international LZ collaboration includes scientists and engineers from 29 institutions in the United States, Portugal, Russia and the United Kingdom.

The next-generation detector, LZ, will consist of a 7-ton liquid xenon target and an active system for suppressing the rate of non-WIMP signals known as background events, both located inside the same water – tank shield used by LUX. This significant increase in detection capability will increase the sensitivity to WIMPs by more than a hundred times.

Another DOE- and NSF-approved project called SuperCDMS-SNOLAB will also be looking for WIMPs, but with a focus on those that are lighter and less energetic than those primarily detectable by the LZ detector. A third project called ADMX-Gen2 is tuned specifically for axions, and will watch for them by monitoring signals stimulated by a strong magnetic field.

"By picking a combination of these WIMP detection techniques that balance the potential sensitivity, the technical readiness, and the cost, the idea is to have the broadest dark-matter detection program possible," says Murdock "Gil" Gilchriese, LZ project scientist and physicist in Berkeley Lab's Physics Division.

"This is great news in the hunt for dark matter," says Kevin Lesko, senior physicist with LUX/LZ, SURF operations manager and from Berkeley Lab's Physics Division. "With our new detector at SURF, we plan on getting the experiment up and running by 2018 and will continue searching with LUX in the interim."

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2.3 / 5 (7) Jul 16, 2014
Hmm, someone voted this article a 2 but didn't write a comment about it. You'd think they'd want to voice their objections/disgruntled thoughts on the matter.

Anywho, this sounds similar to the neutrino detector, how are they different? Size and content of the tank seem to be one, but are there any other subtler differences? Dark matter doesn't emit or absorb light, but can produce it when interacting with regular matter?
3 / 5 (4) Jul 16, 2014
I don't think it's going to work as a "dark matter" experiment. i DO think they are going learn more about WIMPs.
and how much of the universe is composed of dark matter again? I've heard everything between 20 and 90%. just about every article I've ever read on the subject has a different number for the amount of dark matter in the universe.
SnowballSolarSystem _SSS_
1 / 5 (5) Jul 16, 2014
Don't forget the baryonic Bok globule dark-matter candidate composed of invisible molecular hydrogen and helium with just a trace of BBN lithium.
1 / 5 (5) Jul 16, 2014
There is a lot of money wasted in the name of science. Experiments to detect the theoretical WIMP have been ongoing, with no success. And to what avail? How does benefit from Dark Matter studies? What if DM is nothing more than a combination of the optical illusion of the perceived observations of rotating and interacting galaxies whose puzzling behavior lead to crank theories like DM, and the presence of inert elements whose components do not even interact with one another and so which cannot permit the propagation of photonic waves?

Think: Spiral galaxies whose arms spin outward and yet which rotate in the opposite direction, or vice versa? They could lead to erroneous conclusions about the influence of gravity on their behavior.
4.5 / 5 (2) Jul 16, 2014
-- and what is the difference between this experiment and the search for neutrino's --- tank full of liquid in a dark room and if an atom gets hit it gives off light ---- sounds like a neutrino detector to me
5 / 5 (3) Jul 16, 2014
"...and how much of the universe is composed of dark matter again? I've heard everything between 20 and 90%. just about every article I've ever read on the subject has a different number for the amount of dark matter in the universe."

The estimate doesn't vary much between physicists, actually, but confusion among laymen (which includes me) is common, because it's presented in two different ways, depending on the conversation.

Way number 1: What percentage of matter is dark? About 84.5%.

Way number 2: What percentage of *everything* is dark matter? (Everything includes energy not bound into matter, including dark energy.) Answer: about 26.8%.

The proportions aren't terribly controversial. All of the controversy is in the questions, what *are* dark matter and dark energy?

Nobody knows. There's really no evidence for any hypothesis.

Which means that almost all of the universe is made of things we don't understand at all.

Hence - physicists want to find out. Experiments!
1 / 5 (2) Jul 17, 2014
Alas, the WIMP cannot exist, as has been confirmed consistently over 30 years. The reason is its malfunction at galactic scales, as is also well known, but not really taken seriously. The Galaxy's dwarfs lie in a plane, do not come from random directions, as do newly discovered ones. To mention one of the many other problems, this week we saw a post on having 4 times too little UV radiation for the model to work.
Jul 17, 2014
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1 / 5 (2) Jul 19, 2014
Millions more to hunt for the unicorn of modern science. Pathetic!
Jul 19, 2014
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Jul 19, 2014
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Jul 19, 2014
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