New detector will aid dark matter search

Dec 10, 2008 by David Chandler
An inside view of a neutron detector in development at MIT's Laboratory for Nuclear Science. Pappalardo Fellow Jocelyn Monroe, is seen through the detector. Photo / Donna Coveney

(PhysOrg.com) -- Several research projects are underway to try to detect particles that may make up the mysterious “dark matter” believed to dominate the universe’s mass. But the existing detectors have a problem: They also pick up particles of ordinary matter — hurtling neutrons that masquerade as the elusive dark-matter particles the instruments are designed to find.

MIT physicist Jocelyn Monroe has a solution. A new detector she and her students have built just finished its initial testing last week at Los Alamos National Laboratory. When deployed in the next few months alongside one of the existing dark-matter detectors, the new device should identify all of the ordinary neutrons that come along, leaving anything else that the other detector picks up as a strong candidate for the elusive dark matter.

“Dark matter experiments are very hard,” explains Monroe, who worked on the project with undergraduates Dianna Cowern and Rick Eyers and with graduate students Shawn Henderson and Asher Kaboth. “They are looking for a tiny signal, from a phenomenon that happens very rarely,” namely the collision of a dark-matter particle with one of ordinary matter, producing a tiny, brief flash of light.

Such flashes can be detected by putting a tank of liquid deep underground to shield it from most stray particles, then lining the tank with photomultiplier tubes that can pick up even the faintest bursts of light.

The problem is, even buried a mile underground, calculations show such detectors will pick up far more collisions from particles of ordinary matter than from those made of the still-unknown particles of dark matter. To be precise, the ordinary collisions should happen about 10 billion billion times (19 orders of magnitude) more often than the dark-matter collisions. So learning how to rule out those ordinary collisions is the key to finding the unknown matter.

“We’re really trying to characterize the background,” Monroe explains. “We’re making a precise measurement of the energy spectrum of the neutron background.” By understanding the nature and intensity of this background, it will be possible to design more effective shielding material to keep them away from the detectors.

And by running the two detectors at the same time, anytime a signal is seen in the neutron detector, any signal seen simultaneously in the dark-matter detector can be safely ignored. Only when the dark matter detector sees something and the neutron detector doesn’t will there be a chance that one of the elusive dark-matter particles has been found.

Nobody knows what the dark matter is made of, but astronomers are sure it’s there because of the way its gravitational attraction pulls on other, visible matter in space. That allows them to determine just how much of the mystery matter is out there — more than five times as much as the amount of ordinary matter — but not what it’s made of.

Theorists have come up with a variety of candidates, but the leading contenders are a class of subatomic particles known as WIMPS — weakly-interacting massive particles. These are the types of particles, including one called the neutralino, which should be detectable by the deep underground experiments.

“I think probably in the next five years, someone will see a candidate” for a dark-matter particle, Monroe says. Although some experiments have already claimed to see possible evidence of dark matter, so far those claimed results “are surprising and unconfirmed,” Monroe says, and have not been accepted by most scientists.

To test the new detector, Monroe and her students took it to Los Alamos National Laboratory, where it was exposed to a neutron source so that its sensitivity could be precisely calibrated. Once the analysis of that test is completed, the device will be sent out to an underground laboratory, most likely at the planned Deep Underground Science and Engineering Laboratory. This facility, though not funded yet, would be set up in the Homestake Mine, a very deep old gold mining complex in South Dakota, and one of its multidisciplinary goals is provide the world’s deepest location for the detection of cosmic dark matter.

The research is partly funded by the National Science Foundation.

Provided by MIT

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theophys
4 / 5 (1) Dec 10, 2008
Process of elimination, clever.
MrGrynch
1.7 / 5 (6) Dec 10, 2008
Too bad they haven't eliminated the need for dark matter. It's fiction once you factor in the electric forces which are much stronger than gravity.
TimESimmons
2 / 5 (4) Dec 10, 2008
Shall we line up all the theories? Here's mine:-

http://www.presto...ndex.htm
Soylent
5 / 5 (5) Dec 10, 2008
It's fiction once you factor in the electric forces which are much stronger than gravity.


No, the universe is electrically neutral on large scales so you wouldn't expect electric forces to be of any relevance.
theophys
5 / 5 (5) Dec 10, 2008
q] It's fiction once you factor in the electric forces which are much stronger than gravity.


On an individual particle basis, yes, electromagnitism is much much stronger than gravity. Magnatism, however, does not build up in the same way that gravity does. If you have a bunch of particles of the same mass, the overall gravity of the system is that of the combined masses. Magnatism does not stack like this. A thousand magnets of a certain strength combine to formone giant magnet of the same strength.
Plus Soylent is right,
the universe is electrically neutral on large scales
MrGrynch
2 / 5 (3) Dec 10, 2008
If you think the universe is electrically neutral on large scales and that that rules out electrical effects, then you really should see this..

http://www.thunde...sume.htm

Plasma cosmology resolves the need for dark matter or dark energy by examining forces that are already there, but presumed to be insignificant.
TimESimmons
1 / 5 (3) Dec 10, 2008
Amazing MrGrych. I read your linked page carefully, determined to understand and respond to its claims. And what do I find? It actually doesn't say anything. What a waste of words! Except for the starting sentences "The burden of proof is on gravity theorists to explain ...." which is just plain wrong. The burden of proof is on anyone who presents a point of view. My principle objection to the Plasma Cosmology theory is that it claims two incompatible things 1)that the universe is conductive and 2) that separated charges build up within it. Once again I believe the real answer and the evidence is here:-

http://www.presto...ndex.htm
MrGrynch
3 / 5 (4) Dec 10, 2008
The article speaks volumes for the assumptions that are accepted as facts, while a more plausible explanation is staring them in the face, and has been for decades.

You're comments indicate a clear lack of understanding of plasma physics. By definition if the universe is 99.99% plasma (fact), than it IS conductive. As for charges building up, I don't know where you came up with a silly notion like that. Charges build up because of charge separation and in plasmas, charges self separate into double layers. This is known fact. In Space, these double layers twist among each other like braided wires and are called Bikeland Currents. Several of these have already been observed in recent headlines, choosing to call them "magnetic ropes". However, modern theory presumes that magnetic field can be 'frozen into' plasmas, which Hans Alfven warned against in his Nobel acceptance speech which brought the field into existence. You cann't have magnetic fields without electric currents, so these magnetic ropes are Birkeland Currents. they are also responsible for the 'hot spots' seen on so many solar bodies which currently defy explanation. It is presumed to be some form of vulanism, yet they fail to mention this violates their models for solar system formation.

Current theory has failed to prove anything, and its predictive ability is even weaker. Rather than accept that current theory may be wrong, it is patched until it is inconsistent even with itself.

Try reading the hundreds of other examples where current theory fails, yet finds answers in Plasma Cosmology, which is testable in the lab at smaller scales. The beauty of plasma is that effects scale. If you can produce effects at small scale in the lab, there is no reason to believe it cannot happen at much larger scale in the Cosmos.

Look at Peratt's plasma simulations showing that spiral galaxies form naturally through charge separation, without utilizing "dark matter" to explain it.
theophys
5 / 5 (2) Dec 10, 2008
By definition if the universe is 99.99% plasma (fact), than it IS conductive.

I'm gonna have to say ballux. It's true, there is a lot of plasma out there, but that doesn't mean the universe is conductive. Besides, the universe has far more empty space than it does plasma. And we all know that the number one insulator is empty space. Yeah, there's a lot of electricity out there. But it is all local.
axemaster
4.2 / 5 (6) Dec 10, 2008
"If you think the universe is electrically neutral on large scales and that that rules out electrical effects, then you really should see this..

http://www.thunde...sume.htm

Plasma cosmology resolves the need for dark matter or dark energy by examining forces that are already there, but presumed to be insignificant."

This article is a joke, right? Please say yes...

I nearly passed out from lack of oxygen within the first 60 lines or so... Whoever wrote this is, for lack of a better word, a moron. Not only because he doesn't have the SLIGHTEST idea what he's talking about, but also because he tries to make up for it by using words like "Consilience" and "tautologies" to confuse the reader.

So let's break down some of his statements:

"Until the space age, human experience was almost exclusively that of neutral earth, air, fire, and water."

Uh oh... Earth, Air, Fire, and Water? I was under the impression that generally the grouping is: Solid, Liquid, Gas. (Seeing the old EAFW group instantly activated my dumbass alert system)

"Several astrophysicists have told me that, although plasma cosmology appears interesting, they won't consider it until proponents can prove that some mechanism can produce charge separation in space from neutral matter on an astronomically significant scale."

That's a perfectly reasonable statement. But watch what comes next:

"Investigations of plasma phenomena in the past century now confront us with another possibility. We've become aware that most of the observable universe is composed of plasma. The starting condition could just as well be separated charges, and what we observe is the consequential charge combination (not recombination)."

Oh dear. He's just exposed his ignorance to us all. Astronomers do indeed agree that the universe is mostly plasma, but this man seems to think that that somehow proves his "theory" (although the word theory implies something like math, which he clearly doesn't understand). The thing is, plasma is made up of both positive and negative particles, which tend to stay together, so things remain neutral.

Let's continue, shall we?

"Awareness of the bias of familiarity then provokes a second thought. The bias arises not from where we live but from the peculiar limits of our senses. Plasma activity proclaims itself largely in frequencies such as radio and x-ray that lie outside the sensitivities of our senses. We are unfamiliar with plasma because we are blind to it. Modern astrophysicists are in this sense correct to claim that 90% of the universe is undetectable dark substances. Their error is to fill in the blank with mathematical extrapolations from familiar theories and to leave their thinking blind to plasma."

Oh wow. See? He doesn't like math. And we are NOT blind to plasma, astrophysicists have been able to detect it with incredible precision for a very long time now. Please, sir, don't try to argue that we are stupider than you. That's just insulting.

I think it's fair to assume at this point that this man is a QUACK.

That assumption is reinforced by this statement (which he repeats several times, just to hammer it into our skulls).

"Consilience with the already known is a circular argument because our other physical theories are also based on this presumption. After removing tautologies, reasonableness reduces to familiarity and parochialism."

Uh oh... The typical, "think outside the box" argument. One used by all quacks.

To understand more about identifying quacks, read the article linked below. It will amuse you greatly.

http://insti.phys...ack.html
theophys
5 / 5 (3) Dec 10, 2008
axemaster, you win at life. Quite hilarious.
TimESimmons
1 / 5 (3) Dec 11, 2008
Bravo axemaster! Now do a critique of anti-gravity matter. Is it also Quackery?

http://www.presto...ndex.htm
earls
2 / 5 (1) Dec 11, 2008
What evidence is there that the universe is electrically neutral on large scales? Some data would be invaluable.

Googling this question provides many arguments that a universal charge imbalance would impede the Universe from forming and operating as it has today... However, such approaches assume that gravity is in the driver's seat, applying conventional wisdom to the question at hand.

Can we all not agree that current "conventional wisdom" is at least misguided, if not flat out wrong, simply as evidence by the numerous mysteries that lay before us?
theophys
not rated yet Dec 11, 2008
Can we all not agree that current "conventional wisdom" is at least misguided, if not flat out wrong, simply as evidence by the numerous mysteries that lay before us?


Well, it seems to me that the driving force behind the "conventional wisdon" in modern science is what we call logic. So, no. I can't agree. Unless of course you can show me evidense that current scientific methods do not work.
earls
not rated yet Dec 11, 2008
http://en.wikiped...on_curve

LOGICALLY, it was concluded that galactic rotation should fit a specific rotation curve. This was determined to not be the case, casting doubt on the current scientific method and understanding of gravity. As in, IT DID NOT WORK to explain galactic rotation.

So, theo, are you just trying to be obnoxiously inflammatory, or are you just stupid?

Do you need me to troll this site collecting links to all of the other articles about the "mysteries" and "problems" currently facing astronomy and cosmology due to the ignorance that a problem exists in the theory itself?!
theophys
not rated yet Dec 11, 2008
LOGICALLY, the galactic rotations observed befitted objects with more mass than was being observed so it was LOGICALLY concluded that there m ust be something else going on so new theories were created using LOGIC and the SCIENTIFIC METHOD. The theories have been mostly worked out and now await the results of expirimentation to prove or disprove the predictions of said theories. I see absolutely no problem with the scientific method as it stands and we have yet to find a single problem that cannot be approached and hopefully solved using this method of thought.If you would like to provide a replacement that works better than the scietific method, I am all ears...or eyes, as it is.
As for trolling the site, you may attack astronomy and cosmology all you want, but I doubt you can come up with better theories.
earls
not rated yet Dec 11, 2008
The problem is not with the scientific method itself, I never stated that, nor do I know what would possess you to believe I was referring to it. The problem is with the results (or there lack of) - as in "current conventional wisdom."

And that's all fine and good, I happily await the results of the proposed experiments. However, when it returns null results will the scientists be as hasty to dismiss dark matter as they were the aether?

Just how far down the rabbit hole do we go until "enough is enough" to say, "HEY! Let's try something else."
theophys
2 / 5 (1) Dec 11, 2008
LOGICALLY, it was concluded that galactic rotation should fit a specific rotation curve. This was determined to not be the case, casting doubt on the current scientific method and understanding of gravity. As in, IT DID NOT WORK to explain galactic rotation.


That would be why I assumed you had a problem with the scientific method. As for when is enough enough, there are a couple factors that tell us when to stop.
Un) the theory is proved to be so wrong that using it as a model does more harm than good.
Deux) When a new theory that fits observation better and has more predictive power comes along
or Tois) When our sun besomes a red giant, enveloping our planet in a firey death.

And the aether hasn't been given up comepletely. Every decade or so, some nut gets up a following of stupid nuts and they bark about how foolish we are to ignore the aether for a year or so and then settle down for a nap.
Zukoca
not rated yet Dec 12, 2008
Axemaster, the link at the end of your post is invalid.