Seeing the dark: New experiment could finally shed light on the mysteries of dark matter

Oct 25, 2013
Photo shows a prototype device designed by the MIT team to produce a very narrow, high-powered beam of electrons for an experiment called DarkLight. The device was tested at the Jefferson National Accelerator Facility to confirm that it could meet the requirements needed to detect a hypothesized particle based on one theory about the nature of dark matter.

Dark matter, believed by physicists to outweigh all the normal matter in the universe by more than five to one, is by definition invisible. But certain features associated with dark matter might be detectable, according to some of the many competing theories describing this elusive matter. Now scientists at MIT and elsewhere have developed a tool that could test some of these predictions and thus prove, or disprove, one of the leading theories.

The work is described in a paper in the journal Physical Review Letters co-authored by MIT physics professors Richard Milner and Peter Fisher and 19 other researchers.

"We're looking for a massive photon," Milner explains. That may seem like a contradiction in terms: Photons, or particles of light, are known to be massless. That's why they travel at the speed of light—something that, according to Einstein's theory of relativity, is impossible for anything that possesses mass.

However, an exotic particle that resembles a photon, but with mass, has been proposed by some theorists to explain dark matter—whose nature is unknown but whose existence can be inferred from the gravitational attraction it exerts on ordinary matter, such as in the way galaxies rotate and clump together. Now, an experiment known as DarkLight, developed by Fisher and Milner in collaboration with researchers at the Jefferson National Accelerator Laboratory in Virginia and others, will look for a massive photon with a specific energy postulated in one particular theory about dark matter, Milner says.

The idea is more than just a theoretical prediction, he adds: There are hints of such a particle from other experiments, making it worthwhile to pursue a definitive answer. But the previous hints, consisting of what Milner calls "anomalous moments of the muon," do not rise to statistical significance. The DarkLight experiment is designed to provide solid confirmation of the massive photon's existence.

If it does exist, that would represent a major discovery, Milner says. "It's totally beyond anything we understand about the physical world," he says. "A massive photon would be totally different" from anything allowed by the Standard Model, the bedrock of modern , he says.

To prove the existence of the theorized particle, dubbed A' ("A prime"), the new experiment will use a particle accelerator at the Jefferson Lab that has been tuned to produce a very narrow beam of electrons with a megawatt of power. That's a lot of power, Milner says: "You could not put any material in that path," he says, without having it obliterated by the beam. For comparison, he explains that a hot oven represents a kilowatt of power. "This is a thousand times that," he says, concentrated into mere millionths of a meter.

The new paper confirms that the new facility's beam meets the characteristics needed to definitively detect the hypothetical particle—or rather, to detect the two that it decays into, in precise proportions that would reveal its existence. Doing so, however, will require up to two years of further preparations and testing of the equipment, followed by another two years to collect data on millions of electron collisions in the search for a tiny statistical anomaly.

"It's a tiny effect," Milner says, but "it can have enormous consequences for our theories and our understanding. It would be absolutely groundbreaking in physics."

While DarkLight's main purpose is to search for the A' particle, it also happens to be well suited to addressing other major puzzles in physics, Milner says. It can probe the nature of a reaction, inside stars, in which carbon and helium fuse to form —a process that accounts for all of the oxygen that now exists in the universe.

"This is the stuff we're all made of," Milner says, and the rate of this reaction determines how much oxygen exists. While that reaction rate is very hard to measure, Milner says, the DarkLight experiment could illuminate the process in a novel way: "The idea is to do the inverse." Instead of fusing atoms to form oxygen, the experiment would direct the powerful at an oxygen target, causing it to split into carbon and helium. That, Milner says, would provide an indirect way of determining the stellar production rate.

Roy Holt, a distinguished fellow in the physics division at Argonne National Laboratory in Illinois, says this work is "a novel and significant technical development that not only opens a new window to search for a new [particle], but also for new studies in nuclear ." If the planned experiment detects the A' particle, he says, "it would signal that could actually be studied in a laboratory setting."

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

More information: "Transmission of Megawatt Relativistic Electron Beams through Millimeter Apertures" prl.aps.org/abstract/PRL/v111/i16/e164801

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User comments : 25

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vacuum-mechanics
Oct 25, 2013
This comment has been removed by a moderator.
Rutzs
2.3 / 5 (16) Oct 25, 2013
How do I report for spam? This guy constantly links to his own page for ad revenue.
verkle
1.9 / 5 (16) Oct 25, 2013
Rutzs, I agree that Mr. VM does not add much to discussions, and is rather distracting. But, I don't know if your statement of linking for ad revenue is correct. I don't see any ads on his pages.

no fate
4 / 5 (9) Oct 25, 2013
Rutzs, I agree that Mr. VM does not add much to discussions, and is rather distracting. But, I don't know if your statement of linking for ad revenue is correct. I don't see any ads on his pages.



He's trying to sell his theory. Not many takers.
Tektrix
4.2 / 5 (5) Oct 25, 2013
"...Mr. VM does not add much to discussions..."

But his antics here make excellent plot-fodder for a sci-fi short story series. ;)
Shabs42
3.5 / 5 (6) Oct 25, 2013
Rutzs, I agree that Mr. VM does not add much to discussions, and is rather distracting. But, I don't know if your statement of linking for ad revenue is correct. I don't see any ads on his pages.



He's trying to sell his theory. Not many takers.


But, you can click report on the bottom right of his comment. I do on a lot of the spammier ones, hopefully we can hit some sort of tipping point and phys.org can ban a few IP addresses.
Noumenon
2.8 / 5 (27) Oct 25, 2013
Rutzs, I agree that Mr. VM does not add much to discussions, and is rather distracting. But, I don't know if your statement of linking for ad revenue is correct. I don't see any ads on his pages.



He's trying to sell his theory. Not many takers.


But, you can click report on the bottom right of his comment. I do on a lot of the spammier ones, hopefully we can hit some sort of tipping point and phys.org can ban a few IP addresses.


You cannot possibly be negatively effected unless you voluntarily read his posts,... so, once you read "vacuum-mechanics" as the poster, .....simply skip to the next comment.

It's actually much quicker to do this than clicking on 'report' and hoping for thought police to save you from vacuous posts, or going though the effort of posting your complaint.
brt
2.2 / 5 (17) Oct 25, 2013
Well, when I wrote there, that the http://aetherwave...ton.html - apparently many particles are here, but none of them is similar to another ones.


SPEAK-A ENGRISH!
Danie
1.7 / 5 (12) Oct 25, 2013
I, for one, am eager to see the results of this test. Whether they find a photon with mass, or something else completely, a new approach is always a good idea. Perhaps these quantum particles that continuously phase in and out of our dimension causes the force called Dark Matter. Small enough that its not noticeable in atmospheric pressure, but that big empty space out there with no resistance is another story.
John92
3 / 5 (2) Oct 25, 2013
How do I report for spam? This guy constantly links to his own page for ad revenue.

Go over the comment with your cursor and in the bottom right corner you have an option of either quote or report (spam, offensive or inappropriate)
Danie
1.8 / 5 (15) Oct 25, 2013
We humans have always been explorers and tinkerers. This is how we evolve and what drives us. It is a fundamental aspect of humans, to be curious. This wont change, and I dare say finding the Higgs particle payed for that collider so many times over, just to name but one of the amazing things we learned from it, which will have profound influence in our future. No... I absolutely disagree with your post, and think if you wish to complain about any of our tax money going to waste, you should take that to the military sites.
LarryD
1 / 5 (1) Oct 26, 2013
Very difficult, who should get 'this amount' and who shouldn't is always a matter of concern because society dosn't have the funds to reasearch everything it needs to. When it comes to 'national security'...well we can argue about it all day and night but it won't change.
I wonder if the article is suggesting a massive photon at velocity c? Photons do travel at less than c in different mediums so are they looking for a massive photon to identify the medium. If they find a massive photon in a vacuum then this implies that the postulate of SR is not correct.
Kaymen
1.5 / 5 (12) Oct 26, 2013
I rarely post here because the immense amount of petty arguing about competing theories/hypothesis. With all the bickering and name calling I feel like i'm back in grade school. That being said, I would still like to offer an idea of my own in the hopes that those of you with more than two brain cells to rub together may offer some constructive criticism.

My idea is this: there is no such things as dark matter or dark energy. The effects that we observe that lead to thinking they are real are as follows. 1) Photons have mass as they are affected by gravity since gravity and mass seem so intertwined. the larger the mass, the higher the gravity. 2) We cannot see a photon that is traveling away from us. We only observe the small percentage that are aimed in our direction. Thus this matter(photons) appear invisible and only shows an effect through their cumulative gravitational attraction.
Kaymen
1.4 / 5 (11) Oct 26, 2013
contd...

As far as dark energy goes, as gravity drops off according to the inverse square law, photons still travel at the speed of light outward in all directions. Their wavelengths have been stretched during their escape from deep within the gravity well but their speed and energies remain the same. This applies radiation pressure against all other particles (even other photons) that exerts and outward force, causing the observed expansion of the universe as the radiation pressure overcomes gravity at larger distances. Again, we cannot observe these photons if they are not directed towards us.

These are my ideas and I would hope they at least make some sort of sense.
cantdrive85
1.2 / 5 (17) Oct 26, 2013
there is no such things as dark matter or dark energy
If there no such things, then there is no need to write the posts about it like these two above. In astronomy these two terms are phenomenological denominations for two phenomena, which are indeed real and they were even ignored long time with mainstream physics, because they don't play well with mainstream theories. But you're saying instead, that the dark matter is perfectly real and it's formed with normal photons. But in science http://imgs.xkcd....ory.png, what you think about (composition of) things, but which testable predictions you can deduce from it.

DE and DM are ad hoc'd additions to failed theories, a band aid for those with only gravity to explain large scale phenomena.
ubavontuba
1 / 5 (12) Oct 26, 2013
"You could not put any material in that path," he says, without having it obliterated by the beam.
Sounds pretty dangerous. Is the beam entirely contained? How?

JIMBO
not rated yet Oct 26, 2013
IMO, this is a maverick idea, a last-gasp hope for finding a DM candidate particle, unobserved at LHC, and by all expts. to date, particularly XENON, which pretty much closed out the parameter space where a massive DM particle was postulated to be found.
Benni
1 / 5 (12) Oct 26, 2013
"However, an exotic particle that resembles a photon, but with mass, has been proposed by some theorists to explain dark matter—"

Above quote is from the article itself........if it's a photon, it cannot possibly be "an exotic particle" because in such a case it would already be "matter" & inherently have "mass". The language they're using is so ridiculously circular that it is meaningless. In trying to follow their explanation of how a particle resembles a photon, they are contradicting themselves.

Benni
1 / 5 (13) Oct 26, 2013
My idea is this: there is no such things as dark matter or dark energy.


Then how would the excess of measured gravitational field be accounted for?

1) Photons have mass as they are affected by gravity since gravity and mass seem so intertwined. the larger the mass, the higher the gravity.


Photons have what is called "relativistic mass"- when mass is transformed to energy, the amount of mass reduction upon transformation results in a loss of gravity within the remaining quantity of mass, the loss of gravity was carried away by the transformation to energy.Dark energy is simply electromagnetism that is above or below highest or lowest levels of detection with current instrumentation.

2)Thus this matter(photons) appear invisible and only shows an effect through their cumulative gravitational attraction.


Correct, we detect dark energy & mass because both exert gravitational fields, otherwise gravitational lensing of visible light cannot occur.
El_Nose
not rated yet Oct 26, 2013
@JIMBO

The LHC has not really began to look for a DM canindate -- unless looking for anything unusual counts in their quest for the Higg's, which was kept to specific ranges of energy

And the LHC is not up to full power yet, but while the LHC is capable of looking in the 10 Me to 10 Ge range of energy level they are looking for , this experiment is best doen elsewhere as the full energy of the LHC is 14 Te which they have not gotten up to yet and plan on ramping up to after this 16 mo shutdown.
Kaymen
1.3 / 5 (12) Oct 26, 2013
there is no such things as dark matter or dark energy
If there no such things, then there is no need to write the posts about it like these two above. In astronomy these two terms are phenomenological denominations for two phenomena, which are indeed real and they were even ignored long time with mainstream physics, because they don't play well with mainstream theories. But you're saying instead, that the dark matter is perfectly real and it's formed with normal photons. But in science http://imgs.xkcd....ory.png, what you think about (composition of) things, but which testable predictions you can deduce from it.


What I'm trying to say is that there is no need to create some exotic new particle or energy source to describe the observed effects. I really wish I knew the math to explain my thoughts better.
Q-Star
4.2 / 5 (5) Oct 26, 2013
What I'm trying to say is that there is no need to create some exotic new particle or energy source to describe the observed effects.


Ya got it backwards, the observed effects describe & infer the particle. Not the other way around.

I really wish I knew the math to explain my thoughts better.


If ya knew the maths your thoughts on the particle would not be what they are. The maths and the observations beg the particle. These are really smart people involved in this work.

The simple and easy stuff they already thought of and discounted way back when,,, they were in high school and university. Before ya try to tell them they are wrong, it would be worthwhile to learn what they learned so ya could discuss it on their level.
Q-Star
5 / 5 (4) Oct 26, 2013
Their wavelengths have been stretched during their escape from deep within the gravity well but their speed and energies remain the same.


Increasing the wavelength IS a reduction in energy.

This applies radiation pressure against all other particles (even other photons) that exerts and outward force,


(even other photons) No, photons in this environment pass right through each other, in this sort of environment photons do not interact with other photons, they pass right through each other.

causing the observed expansion of the universe as the radiation pressure overcomes gravity at larger distances.


Radiation pressure diminishes more quickly than gravity as the distance increases. Otherwise stars couldn't form,,,,,, and achieve hydrostatic equilibrium.

Again, we cannot observe these photons if they are not directed towards us.


But the ones we can't observe must act the same as the ones we do see. Physics is physics regardless of direction.
Zephir_fan
Oct 26, 2013
This comment has been removed by a moderator.
LarryD
not rated yet Oct 27, 2013
I'm all for experiments that would investigate DM, but so soon after the Higgs Nobel I wonder if we are see something like a search for photon counterpart of the Higgs particle...just a thought.
LarryD
not rated yet Oct 27, 2013
Franklins, yes I realise the difference in Higgs and photon. I was really talking about the overall experiment itself rather than the object of the search.
Osiris1
1 / 5 (2) Oct 28, 2013
"VM"...what "VM". He must have jerked his post.....or the site did it. Off 'topic', but fusion was mentioned as an alternative study topic for this. Device is claimed to be able to initiate carbon-helium fusion. That takes a lot of energy. Maybe it can do H-H fusion too and generate energy.... Just a thought.