Hunt for dark matter takes physicists deep below earth's surface, where WIMPS can't hide

August 7, 2014 by Margaret Allen, Southern Methodist University

Dark matter makes up much of the universe, and surrounds us all like an invisible soup. Physicists have hunted dark matter particles for decades, but they continue to elude observation.

Now a major international experiment aimed at discovering could be constructed and operational by 2018, according to the consortium of scientists on the experiment known by its acronym, SuperCDMS SNOLAB.

With SuperCDMS SNOLAB, physicists will go deeper below the surface of the earth than earlier generations of the experiment. Deep underground, scientists use the earth as a shield to block out particles that resemble dark matter, making it easier to see the real thing.

Physicists have begun research and design and are building prototypes for the next-generation SuperCDMS, known by its full name as the Super Cryogenic Dark Matter Search. It will be located at SNOLAB, an existing underground science laboratory in Ontario, Canada, said physicist Jodi Cooley, a SuperCDMS scientist.

As an experimental particle physicist, Cooley heads the dark matter project team at Southern Methodist University, Dallas, and is a designated principal investigator, or lead scientist, on the SuperCDMS experiments.

Research and design of SuperCDMS SNOLAB is slated to continue through 2015, with fabrication in 2016 and 2017. The experiment could be ready for operational testing by 2018, Cooley said.

DOE and NSF announce support for SuperCDMS SNOLAB

The U.S. Department of Energy and the National Science Foundation recently announced they will fund SuperCDMS SNOLAB—as well as two other unrelated dark matter experiments—as part of a committed U.S. scientific focus on furthering investigation into elusive dark matter. The agencies previously funded the predecessors to SuperCDMS SNOLAB, known as SuperCDMS Soudan and CDMS.

"This is a very exciting time in our field, and I think the United States is well-positioned to play a key role," said Cooley, an associate professor in SMU's Department of Physics. "The three experiments chosen, SuperCDMS, LZ and AMDX, are complementary and together provide sensitivity to a large variety of potential dark matter candidates. In particular, SuperCDMS provides unprecedented sensitivity to light dark-matter candidates."

SuperCDMS SNOLAB is a collaboration of physicists from 21 institutions in the United States, Canada and Europe.

The U.S. Department of Energy and the National Science Foundation recently announced they will fund SuperCDMS SNOLAB—as well as two other unrelated dark matter experiments—as part of a committed U.S. scientific focus on furthering investigation into elusive dark matter. The agencies previously funded the predecessors to SuperCDMS SNOLAB: SuperCDMS Soudan and CDMS.

Dark matter—the next unsolved mystery, and a key to the Universe

There has long been evidence that dark matter exists and is a large part of the matter that makes up the Universe. A handful of experiments around the globe, including SuperCDMS Soudan and CDMS II, use different methods to focus on the hunt for dark matter.

The design of SuperCDMS SNOLAB, which is among the world's leading dark matter projects, enables it to look for WIMPS, short for weakly interacting massive particles.

WIMPS are a generic class of dark matter, with an unknown mass that could be either "light" or "heavy." SuperCDMS has unprecedented sensitivity to the light mass, sometimes called low mass, WIMPS. The LZ experiment will have unprecedented sensitivity to heavy mass, or high mass, WIMPS. AMDX looks for a different type of dark matter called an axion.

CDMS and SuperCDMS Soudan also focus on lower mass dark matter.

Deep below the ground, to block out distractions

SuperCDMS SNOLAB will be constructed 6,800 feet underground—much deeper than CDMS or SuperCDMS Soudan, which are 2,341 feet below the earth in an abandoned underground iron mine near Soudan, Minn. Depth decreases what Cooley refers to as the "background noise" of other particles that can mimic dark matter or cloud an observation.

DOE and NSF announced they would fund dark matter experiments in the wake of recommendations in May from their Particle Physics Project Prioritization Panel, a task force of the DOE and NSF made up of U.S. physicists.

In its report, the panel didn't specify any particular dark matter experiments for funding, but broadly concluded that investment in the search for dark matter is key for the United States to maintain its status as a global leader in addressing the most pressing scientific questions.

Total projected cost for SuperCDMS SNOLAB is about $30 million.

SuperCDMS: How it works

The heart of SuperCDMS is an array of 42 detectors the size of hockey pucks, stacked atop one another in a copper canister encased in a large cooling tower. Their purpose is to capture any evidence of dark matter with their silicon and germanium surfaces, which are cooled to near absolute zero to measure single particle interactions.

SuperCDMS SNOLAB is a ramped-up version of its predecessors, with 10 times the sensitivity to detect a full range of WIMPS, from 1 to 1,000 gigaelectronvolts.

SMU's SuperCDMS project team is participating in the design and development of the shielding at SuperCDMS SNOLAB and the selection of radio-pure materials that will be used in the construction of the experiment. The shielding's purpose is to shield the detectors from background particles—the interaction signatures of neutrons—that can mimic the behavior of WIMPS.

SMU's dark matter research is funded through a $1 million Early Career Development Award that Cooley was awarded in 2012 from the National Science Foundation.

Fermi National Accelerator Laboratory (Fermilab) and SLAC National Laboratory are the lead laboratories on SuperCDMS Soudan and contribute scientific staff, project management, and engineering and design staff.

Besides SMU and Fermilab, institutions with scientists on SuperCDMS include the California Institute of Technology, Massachusetts Institute of Technology, Queen's University, Texas A&M University, University of California-Berkeley, University of Florida, Centre National de la Recherche Scientifique-LPN, National Institute of Standards and Technology, Santa Clara University, Stanford University, Universidad Autonoma de Madrid, University of Colorado, University of Minnesota, Pacific Northwest National Laboratory, SLAC/Kavli Institute for Particle Astrophysics and Cosmology, Syracuse University, University of British Columbia, University of Evansville and the University of South Dakota.

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SnowballSolarSystem _SSS_
1 / 5 (1) Aug 07, 2014
I thought CDM was in the halo, not underground.

Alternatively, if cold dark matter is invisible baryonic molecular hydrogen and helium globules that condensed by phase-change hydrogen reionization in the early universe, then we'll have to tune our radio telescopes to find light-year scale globules of H2 at 10 K in the Galactic halo.

Bok globules, then, are ancient globules recently contaminated by stellar metallicity in the spiral arms, rendering them opaque, and outgassing Bok globules form (giant) molecular clouds, not the other way around.

Primordial (Bok) globules = cold dark matter
Aug 07, 2014
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SnowballSolarSystem _SSS_
1 / 5 (1) Aug 08, 2014
Hydrogen ionization promoting core collapse in stars today (Larson 1969) may be an almost perfect analogy for hydrogen ionization promoting collapse into (Bok) globules 379,000 years after the big bang.

The next step is to figure out the formation of the first Population III stars, which could be as simple as continued gravitational collapse of globules larger than a given mass, say larger than 200 solar masses. This would make stars and globules an almost perfect analogy with greater mass compensating for higher ambient temperature..
1 / 5 (1) Aug 08, 2014
Let's forget that WIMPs have long been ruled out by their failures at the galactic scale and inside the Galaxy. The show must go on.
1 / 5 (3) Aug 08, 2014
If only the physicists would dedicate the same energy for finding of cold fusion, replication of antigravity drives and beams. In addition, these latest ones are very close to their actual target, i.e. the dark matter particles. In this case the stupidity of people gets multiplied with their ignorance.
5 / 5 (1) Aug 08, 2014
Outer space is full of radioactivity, solar winds and gamma ray flashes which would represent the disturbing background - whole the above article is about it...;-) Anyway, it's much easier to prepare them in the lab, as Tesla already observed before one hundred of years like the needle-like sensation. Probably the simplest arrangement, how to generate them.
5 / 5 (1) Aug 08, 2014
By this experiments, the pair of magnets in monopole arrangement can be not only used for scalar waves generation, but for detection of changes in their flux around Sun as well. In general, the scalar waves require the establishing of energy density gradient in vacuum (the charged capacitor, the magnets attached, whatever) which represents a "paddle" for vacuum fluctuations. The fast motion of such a paddle induces a drift and collective motion of them. Whole this process is similar to generation of underwater vortices at the water surface. Most effective "paddles" are the superconductor and possibly graphene sheets, where the electrons are already compressed against each other. The bringing of voltage pulse to such a material generates a beam of scalar waves, which is propagating at large distance.
5 / 5 (1) Aug 08, 2014
The reactive force formed during bringing the scalar wave solitons into motion is the basis of so-called reactionless drives. The classical arrangement is presented here: it's formed with capacitor, to which magnetic pulse from electromagnet is introduced. The capacitor charge creates a energy density gradient, magnetic field (turbulence of vacuum) brings it into motion. So called the Woodward drive works at very similar principle, it just uses a periodically alternating voltage powering both capacitor, both electromagnet, so that the semi-continuous thrust is achieved. Every such a drive must generate a flux of dark matter particles, which should be detectable by their mechanical action with using of detector based on similar principle, like this one which has generated them: the superconductive layer, with pair of magnets or with charged capacitor.
SnowballSolarSystem _SSS_
1 / 5 (2) Aug 08, 2014
Let's forget that WIMPs have long been ruled out by their failures at the galactic scale and inside the Galaxy. The show must go on.

Besides which, WIMP models are based on fanciful supersymmetric particles not predicted in the standard model of quantum mechanics.
Aug 09, 2014
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1 / 5 (1) Aug 10, 2014
occam's razor obviates the complex theoretical solution. Funny that an invisible undetectable heavy but not weighable object is the simple fix. I know math says so, but physics seems to have the trouble of making it clear.
Aug 10, 2014
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SnowballSolarSystem _SSS_
1 / 5 (1) Aug 10, 2014
I know math says so, but physics seems to have the trouble of making it clear.
It actually doesn't, the scientists are looking for SUSY particles across whole mass spectrum in the same way, like for Higgs http:// - most of which contain continuous parameters whose values aren't calculable right now - that the whole interval is covered almost uniformly.

Lest the success of finding the Higgs boson go to anyone's head, the Higgs boson completes the Standard Model of quantum physics without fanciful SUSY particles. It's quite a stretch to extend the standard model just to explain dark matter.

Are there any observational indications of supersymmetry other than unexplained X-rays findings that keep popping up in CDM articles?

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