Researchers propose gold and DNA based dark matter detector

Jul 03, 2012 by Bob Yirka report
ssDNA/Au Tracking Chamber: A WIMP from the Galaxy scatters elastically with a gold nucleus situated in a thin gold foil. The recoiling Au nucleus traverses hanging strings of single stranded DNA, and severs any ssDNA it hits. The location of the breaks can be found by amplifying and sequencing the fallen ssDNA segment, thereby allowing reconstruction of the track of the recoiling Au nucleus with nanometer accuracy. Image: arXiv:1206.6809v1

(Phys.org) -- One of the precepts of scientific theory is that at some point, physical evidence should become available to prove it true. In physics this is an ongoing process in many areas of study, one of which is the detection and measurement of so called dark matter. Most astrophysicists agree it exists, yet no one has been able to definitively prove it though the presentation of physical evidence. While there are some ongoing projects attempting to do just that, the results have not been strong enough to offer proof. To overcome that problem a team of physicists and biologists have proposed a new type of detector based on a thin sheet of gold with many strands of DNA dangling below. The idea the team says in its paper uploaded to the preprint server arXiv, is to follow the path of a gold nucleus after being struck by a dark matter particle as it makes its way through strands of DNA, severing them as it goes.

, the theory goes, is all around us, but we can’t see it or detect it using conventional means. Scientists believe it’s moving though, from the center of the universe towards us. The best analogy is water, in a stream; we’re like an island in it as is the sun. Thus, because we orbit the sun, and because our planet spins, we ought to be facing upstream sometimes and downstream others. That’s the basis of any dark matter detector, to first detect the weakly interacting massive particles, or WIMPs as researchers call them, and then to measure the amounts of them over the course of a day, or year to see if they conform to theory.

One way to build such a detector this new team says, is to dangle a dense forest of DNA strands from a of gold. The idea is that when a WIMP strikes one of the gold atoms, its nucleus will be sent crashing down through the mass of DNA strands breaking the ones it strikes. Then, because each DNA strand would have a unique marker at its end, researchers could, by collecting the broken strands, figure out the trajectory of the nucleus though the strands and likewise that of the WIMP that struck it. Such a detector would go a long way towards proving that theories about dark matter are true.

Unfortunately, it’s not as simple as all that, because building such a detector would be a feat in and of itself. Making DNA strands that would be long enough to work in such a detector, for example, would be a challenge as would getting them all to align in a meter square trap and to dangle straight down instead of curling up.

On the other hand, the researchers say building such a detector would cost far less money than other efforts underway, and the detector once built would be far more accessible since it could be used at room temperature. Plus, if it worked, the team that built it would almost certainly go down in history as the scientists that finally proved that dark matter is real.

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More information: New Dark Matter Detectors using DNA for Nanometer Tracking, arXiv:1206.6809v1 [astro-ph.IM] arxiv.org/abs/1206.6809

Abstract
Weakly Interacting Massive Particles (WIMPs) may constitute most of the matter in the Universe. While there are intriguing results from DAMA/LIBRA, CoGeNT and CRESST-II, there is not yet a compelling detection of dark matter. The ability to detect the directionality of recoil nuclei will considerably facilitate detection of WIMPs by means of "annual modulation effect" and "diurnal modulation effect". Directional sensitivity requires either extremely large gas (TPC) detectors or detectors with a few nanometer spatial resolution.
In this paper we propose a novel type of dark matter detector: detectors made of DNA could provide nanometer resolution for tracking, an energy threshold of 0.5 keV, and can operate at room temperature. When a WIMP from the Galactic Halo elastically scatters off of a nucleus in the detector, the recoiling nucleus then traverses thousands of strings of single stranded DNA (ssDNA) (all with known base sequences) and severs those ssDNA strands it hits. The location of the break can be identified by amplifying and identifying the segments of cut ssDNA using techniques well known to biologists. Thus the path of the recoiling nucleus can be tracked to nanometer accuracy. In one such detector concept, the transducers are a few nanometer-thick Au-foils of 1m times1m, and the direction of recoiling nuclei is measured by "DNA Tracking Chamber" consisting of ordered array of ssDNA strands. Polymerase Chain Reaction (PCR) and ssDNA sequencing are used to read-out the detector. The detector consists of roughly 1 kg of gold and 0.1 kg of DNA packed into (1m)^3. By leveraging advances in molecular biology, we aim to achieve about 1,000-fold better spatial resolution than in conventional WIMP detectors at reasonable cost.

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User comments : 17

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Jitterbewegung
1.3 / 5 (7) Jul 03, 2012
Where do these scientist believe the center of the universe is?
What is their alternative theory to the big bang?
Pirs01
1.5 / 5 (4) Jul 03, 2012
"Scientists believe its moving though, from the center of the universe towards us."

I'm confused. I thought that the best currently available data tells us that the universe is flat and so infinite? If so what is this "center of the universe" author is talking about?
Bowler_4007
3 / 5 (3) Jul 03, 2012
"Scientists believe its moving though, from the center of the universe towards us."

I'm confused. I thought that the best currently available data tells us that the universe is flat and so infinite? If so what is this "center of the universe" author is talking about?

Your logic doesn't follow, a table is flat is that also infinite? even something such a mobius strip is finite it just doesn't have a definable start or end
antialias_physorg
5 / 5 (5) Jul 03, 2012
Where do these scientist believe the center of the universe is?

Since we're talking about inflation (and not explosion - which is a common misconception when people talk about the 'big bang') the center of the universe is everywhere.
The usual (2D) analogy is to think of the universe as being the surface of a balloon. At first it has size zero then it gets inflated. All points are therefore (still) the center. Remember: inflation is NOT motion.

BTW: This is why we see radiation from the cosmic microwave background - which is the 'afterglow of the big bang' - come from all directions. If it had been an explosion we'd only see it come from one direction.

What is their alternative theory to the big bang?

There are a number. But none make as much sense as the big bang at present.

As for the article: I'm really not certain how they'd distinguish WIMP interactions from interactions of the gold particles with other stuff (e.g. gammas, or -if shielded- neutrinos)
antialias_physorg
5 / 5 (6) Jul 03, 2012
BTW: the article on arxiv makes no mention of Dark matter "moving from the center of the universe towards us."
http://arxiv.org/...09v1.pdf

They talk about moving relative to the dark matter motion in the galaxy, not the universe.
Torbjorn_Larsson_OM
4.5 / 5 (2) Jul 03, 2012
Dreadful article: "prove", "true", "definitely" and "the center of the universe".

We have definitely enough unambiguous evidence testing (so "proved" in the empirical sense) that dark matter and its gravitational influence is a fact (and so "true" in the empirical sense).

In the same way that several independent observations of relativity provides enough unambiguous evidence testing that spacetime and its curvature is a fact. No other theory can compete (so "definitely" in the empirical sense), and people are trying to pin down DM density as much as ST gravitational waves.

Having a local observation is of course much more predictive on masses and other characteristics and less extensive on eliminating contenders, so the effort is well worth it.
Torbjorn_Larsson_OM
2.5 / 5 (2) Jul 03, 2012
My favorite expansion analogy, since the standard cosmology is flat and we don't need to worry about the global topology, is that of a raising raisin bread. The raisins are galaxy analogues, galaxies held together by local gravity resisting the expansion as much as the raisins are held together by chemical EM forces, and follows the expanding dough which expands equally in every point.

Make the dough so large that you don't care about the closure (crust), and it's a fair analogy.

Your baking may vary, of course. (I suggest longer times and lower heat for large breads. =D)
El_Nose
2.5 / 5 (2) Jul 03, 2012
it thought WIMPS were weakly interacting -- how much gold would be needed -- how much DNA
antialias_physorg
3 / 5 (1) Jul 03, 2012
it thought WIMPS were weakly interacting -- how much gold would be needed -- how much DNA

Depends on how long you're willing to wait before analysis. But since they only require a monolayer of gold - not much of that (even if the detector were huge). You'd need a substantial amount of DNA - but that woud probably be less of an issue.

I wonder how they plan on evaluating the analysis. Seems like you'd need to dismantle it all to check each DNA strand.
SatanLover
not rated yet Jul 03, 2012
Do you trust a Belgian catholic priest?
Jitterbewegung
1 / 5 (1) Jul 03, 2012
Ah, so it's the writer of the article that is the quack and is making up theories to ruin the work of the scientists. Why would physorg publish this center of the universe rubbish as if a scientist wrote
it. Why not withdraw the article, expose the writer as a crackpot, say sorry to everyone who was misinformed and rewrite the article using someone else?
Urgelt
not rated yet Jul 03, 2012
Anti, I reckon they'll want to put such a detector deep underground in a low-radiation-emitting rock formation. That'll screen out some non-WIMP interactions. That won't screen out neutrinos, but in theory, they ought to be able to distinguish neutrino interactions (if they can see any at all with that kind of detector, which I, happy in my ignorance, profoundly doubt).

I agree with other commenters concerning the rather awful science writing in this article.
vacuum-mechanics
1 / 5 (2) Jul 03, 2012
By the way, talking about dark matter, it is interesting to note that according to this unconventional idea below, actually dark matter is just the manifest of rotating stress within the dark energy of vacuum space medium!

http://www.vacuum...id=14=en
dirk_bruere
not rated yet Jul 04, 2012
Keeping the DNA straight could be accomplished by putting the whole arrangement in a static electric field
Torbjorn_Larsson_OM
1 / 5 (1) Jul 05, 2012
@ SatanLover:

Fallacy of ad hominem by way of poisoning the well. It doesn't matter where a theory originated if it works.

Btw, standard inflation cosmology basically predicts what the original big bang singularity originators believed is likely wrong - inflation doesn't easily have only "a" singularity.

@ Jitterbewegung:

Certainly you run the risk of having cranks put out press releases (has happened), get papers through journals (has happened) or writing articles based on imaginary press releases (has happened). That said, the risk is low in general outside crank web sites, and especially on these known science outlets.

And this is a many author detection concept paper - it is likely legit.

@ vacuum-mechanics:

But that isn't dark *matter*, which we know need to be cold, dark and particulate. So it's worthless on DM and so uninteresting. Sorry.
C_elegans
not rated yet Jul 08, 2012
I'm a biologist, not a physicist. ssDNA is notoriously sticky. Why wouldn't they use dsDNA? It seems like the ssDNA would simply anneal to neighboring strands and make a mess.
C_elegans
not rated yet Jul 08, 2012
0.1kg of DNA is a lot of DNA. Obtaining a material with that much DNA of known sequence sounds like a very challenging informatics problem.

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