Physicists describe new dark matter detection strategy

November 1, 2017 by Kevin Stacey, Brown University
Physicists describe new dark matter detection strategy
A proposed dark matter detector using superfluid helium might detect particles with much lower mass than most current detectors. Credit: Maris/Seidel/Stein/Brown University

Physicists from Brown University have devised a new strategy for directly detecting dark matter, the elusive material thought to account for the majority of matter in the universe.

The new strategy, which is designed to detect interactions between dark matter and a tub of , would be sensitive to particles in a much lower mass range than is possible with any of the large-scale experiments run so far, the researchers say.

"Most of the large-scale dark matter searches so far have been looking for particles with a mass somewhere between 10 and 10,000 times the mass of a proton," said Derek Stein, a physicist who co-authored the work with two of his Brown University colleagues, Humphrey Maris and George Seidel. "Below 10 proton masses, these experiments start to lose their sensitivity. What we want to do is extend sensitivity down in mass by three or four orders of magnitude and explore the possibility of dark matter particles that are much lighter."

A paper describing the new detector is published in Physical Review Letters.

Missing matter

Though it has not yet been detected directly, physicists are fairly certain that dark matter must exist in some form. The way in which galaxies rotate and the degree to which light bends as it travels through the universe suggest that there's some kind of unseen stuff throwing its gravity around.

The leading idea for the nature of dark matter is that it's some kind of particle, albeit one that interacts very rarely with ordinary matter. But nobody is quite sure what a dark matter particle's properties might be because nobody has yet recorded one of those rare interactions.

There's been good reason, Stein says, to search in the mass range where most dark matter experiments have focused thus far. A particle in that mass range would tie up a lot of loose theoretical ends. For example, the theory of supersymmetry—the idea that all the common particles we know and love have hidden partner particles—predicts dark matter candidates of the order of hundreds of proton masses.

But the no-show of those particles in experiments so far has some physicists thinking about how to look elsewhere. This has led theorists to propose models in which dark matter would have much lower mass.

A new approach

The detection strategy that the Brown researchers have come up with involves a tub of superfluid helium. The idea is that dark matter particles passing through the tub should, on very rare occasions, smack into the nucleus of a helium atom. That collision would produce phonons and rotons—tiny excitations roughly similar to sound waves—which propagate with no loss of kinetic energy inside the superfluid. When those excitations reach the surface of the fluid, they'll cause helium atoms to be released into a vacuum space above the surface. The detection of those released atoms would be the signal that a dark matter interaction has taken place in the tub.

"The last bit is the tricky part," said Maris, who has worked on similar helium-based detection schemes for other particles like solar neutrinos. The collision of a low-mass might result in only a single atom being released from the surface. That single atom would carry only about one milli-electron volt of energy, making it virtually impossible to detect through any traditional means. The novelty of this new detection scheme is a means to amplify that tiny, single-atom energy signature.

It works by generating an electric field in the vacuum space above the liquid using an array of small, positively charged metal pins. As an atom released from the helium surface draws close to a pin, the positively charged tip will steal an electron from it, creating a positively charged helium ion. That newly created positive ion would be in close proximity to the positively charged pin, and because like charges repel each other, the ion will fly off with enough energy to be easily detectable by a standard calorimeter, a device that detects a temperature change when a particle runs into it.

"If we put 10,000 volts on those little pins, then that ion going is going to fly away with 10,000 volts on it," Maris said. "So it's this ionization feature that gives us a new way to detect just the single helium atom that could be associated with a dark matter interaction."

Sensitive at low mass

This new kind of detector wouldn't be the first to use the tub-of-liquid-gas idea. The recently completed Large Underground Xenon (LUX) experiment and its successor, LUX-ZEPLIN, both use tubs of xenon gas. Using helium instead provides an important advantage in looking for particles with lower mass, the researchers say.

For a collision to be detectable, the incoming particle and the target atomic nuclei must be of compatible mass. If the incoming particle is much smaller in mass than the target nuclei, any collision would result in the particle simply bouncing off without leaving a trace. Since LUX and L-Z are intended for the detection of particles with mass greater than five times that of a proton, they used xenon, which has a nucleus of around 100 proton masses. Helium has a nuclear mass only four times that of a proton, making a more compatible target for particles with much less mass.

But even more important than the light target, the researchers say, is the ability of the new scheme to detect only a single atom evaporated from the helium surface. That kind of sensitivity would enable the device to detect the tiny amounts of energy deposited in the detector by particles with very small masses. The Brown team thinks its device would be sensitive to masses down to about twice the of an electron, roughly 1,000 to 10,000 times lighter than the particles detectable in large-scale dark experiments so far.

Stein says that the first steps in actually making such a detector a reality will be fundamental experiments to better understand aspects of what's happening in the superfluid and the precise dynamics of the ionization scheme.

"From those fundamental experiments," Stein says, "we would craft designs for a bigger and more complete experiment."

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

More information: Humphrey J. Maris et al, Dark Matter Detection Using Helium Evaporation and Field Ionization, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.119.181303

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NoStrings
1 / 5 (8) Nov 01, 2017
"From those fundamental experiments," Stein says, "we would craft designs for a bigger and more complete spirits of dead detection experiment."
As long as someone is paying.
etudiant
4.2 / 5 (5) Nov 02, 2017
The experiment seems to assume that the only helium atoms that escape are those liberated by dark matter collisions.
Surely there is some evaporation as well, plus presumably other interactions with cosmic rays and other natural radioactivity. So how does the apparatus differentiate among these?
dogbert
2.4 / 5 (9) Nov 02, 2017
We will apparently continue to look for imaginary matter as long as there is funding for it and funding does not show signs of lessening.
KelDude
2 / 5 (8) Nov 02, 2017
Dark matter and Dark energy are just a figment of someone's imagination. Don't know what you're looking at or what's causing an "affect", may as well dream up dark stuff. What hogwash.
fthompson495
1 / 5 (4) Nov 02, 2017
There is evidence of the strongly interacting, smoothly distributed, supersolid dark matter every time a double slit experiment is performed, as it is the dark matter that waves.
antialias_physorg
5 / 5 (9) Nov 02, 2017
Dark matter and Dark energy are just a figment of someone's imagination.

They are labels for observed effects. So no, they are not a 'figment of someones imagination' but based on hard data.

Now, *what* they are is still up for grabs. Something is causing these observed effects. Whether it be particles or something else. But the labels 'dark matter' or 'dark energy' themselves do not exclude any particular interpretation. They are just placeholder terms. Don't get hung up on the words 'matter' or 'energy' in them.
(It's a bit like particle/wave duality in quantum physics. When someone gets hung up on the words 'particles' or 'wave' as they know them from everyday experience they're already missing the point)
dogbert
3.5 / 5 (2) Nov 02, 2017
antialias_physorg,
They are labels for observed effects.


After years of searching for dark matter and finding none, some people are saying that they really are using the term as a place holder. This is not the case. People are continuing to try to find actual dark matter. This article is just another of many schemes to find this imaginary substance.

If we were to use a place holder, the term would be something on the order of 'gravitational anomaly' because the effects of gravity do not match our models of gravity.

When all these scientists are looking for dark matter, they are really looking for dark matter.

antialias_physorg
5 / 5 (9) Nov 03, 2017
People are continuing to try to find actual dark matter.

Because the observed effect is easiest explained by some form of matter. Checking the easy theories first is just prudent. Science is like that - you never really know beforehand what will be the answer, so you go check off all the possibilities that come to mind in order of likelihood and complexity of experimental apparatus (read: cost). There are other theories, but for some we don't even know how to test.

Note that the idea of very weakly interacting matter isn't as far fetched as some might think. We know that neutrinos exist and they interact hardly at all (and neutrinos were posited well before they were discovered, too).

If we were to use a place holder, the term would be something on the order of 'gravitational anomaly'

Since the origin of the term is about 150 years back you might take it up with Lord Kelvin (or 100 years back depending which part of the origin story you like best).
Da Schneib
5 / 5 (6) Nov 03, 2017
Minor quibble, @antialias, when Fritz Zwicky discovered DM in 1933 in the Coma Cluster using the virial theorem, he called the missing mass "dunkle Materie" literally "dark matter."
antialias_physorg
5 / 5 (7) Nov 03, 2017
A) The dark matter based explanation violates observations from its very beginning, because no matter behaves so

What exactly are you referring to that matter does not behave like? How does it violate existing theories of matter, exactly?

The testing of 'easiest" theories may not be this cheapest one for tax payers at the end.

Unless you have some magical insight into what the 'correct' test is that wil instantaneously lead to he right answer there's no other way. if oyu do then you should publish (seriously)...because that's what journals are for.

Ironically the easiest models of dark matter based on normal form of matter weren't even tested yet.

Such as...?
Da Schneib
5 / 5 (4) Nov 03, 2017
The dark matter based explanation violates observations from its very beginning
This is profoundly ignorant. The very beginning of dark matter was the discovery in 1933 by Fritz Zwicky that the Coma cluster didn't have enough visible mass for the galaxies in it to orbit the way they do according to the virial theorem.

If you think you know enough to make a statement like this, please explain the virial theorem for us all.
Benni
2 / 5 (4) Nov 04, 2017
Sure Schneibo, the virial theorem states that, for a stable, self-gravitating, spherical distribution of equal mass objects (stars, galaxies, etc), the total kinetic energy of the objects is equal to minus 1/2 times the total gravitational potential energy.

The very beginning of dark matter was the discovery in 1933 by Fritz Zwicky


No Scneibo that is not where it started, it started with zany Zwicky FIRST theorizing Spiral Galaxies don't implode due to a counter gravitational force that exists beyond the periphery of the spiral arms, since then ONLY baryonic matter halos have been discovered where Zwicky said we'd find DM & there's a lot of gravity to be found in those baryonic halos often extending to the nearest galaxies.

Ever notice all those huge Elliptical galaxies in that Coma cluster, every one of them hundreds of times larger than our Milky Way & they contain 2/3 of the mass of the Universe, yeah a lot of mass there explaining the virial theorem.
RNP
3.7 / 5 (6) Nov 04, 2017
@Benni
Amazing! You have found another scientific buzz-word and completely garbled it.

1) Zwicky never theorized that "Spiral Galaxies don't implode due to a counter gravitational force ". First, he never worked on spiral galaxies and never published anything about them. Second, DM is not a "counter-gravitational force", as, were it absent, galaxies would expand not contract.

2) All elliptical galaxies have been shown to require DM to explain their dynamics just as much as spiral galaxies. Just look up velocity dispersion in elliptical galaxies in some serious scientific papers (or given your obvious lack of a scientific education), Google it.

3) It makes NO sense to claim that elliptical galaxy mass can "explain the virial theorem", which applies to all gravitationally bound systems independently.

Every time you try to convince us of your education and intelligence you make your ignorance clearer.
dogbert
not rated yet Nov 04, 2017
antialias_physorg,
People are continuing to try to find actual dark matter.


Because the observed effect is easiest explained by some form of matter.


But it is not. We have been searching for dark matter for over 80 years. We have not found a single particle of dark matter in all that time. Our standard model does not contain dark matter. None of our high energy colliders have found a single particle of dark matter.

Should we continue to search for dark matter for another 80+ years because it is the easiest path or should we try to discover why our models do not match our observations?

I think the obsession with finding dark matter is blinding us to any other explanation for the observer anomalies.

Hyperfuzzy
1 / 5 (2) Nov 04, 2017
I love the bull$hit. Charge is the only thing that exist and we and everything else is made from it. Charge is the charge's field, and is conserved. Think, I've covered this before the Nobel committee sanctioned gravitational waves? I'll save you the redundancy of disproving Einstein 'cause that's simply nonsense and no PhD is worthy that also sanctions it. So space is filled with the field from every charge at every point. It's OK. I know how hard it is to admit stupid. No I don't. I've never been that stupid! Dark matter? LOL! Get your money back for your PhD. OK, trolls speak your nonsense!
Hyperfuzzy
1 / 5 (2) Nov 04, 2017
Gravity is the DC Field; Light is the sinusoidal; everything else some event. Dark matter, particles, mass, do not exist. i.e. Post grad is nonsense.

When you evolve to be able to think, you might learn how to sail the sea, i.e. an infinite field.
Hyperfuzzy
1 / 5 (2) Nov 04, 2017
Maybe your assumption that space is empty is your error. No empty space exist. Please save your stupid remarks; they will be used for laughter in future high school physics classes.
Shabs42
5 / 5 (2) Nov 04, 2017
Anybody want to ignore the normal drudgery and answer the question in the second comment? That was my biggest question after reading the article as well. My first guess was that based on the weight of the helium atoms they'll be able to tell the exact size/form of the particle that interacts with them, so if it's anything unusual it would stand out.
Whydening Gyre
5 / 5 (1) Nov 04, 2017
The very beginning of dark matter was the discovery in 1933 by Fritz Zwicky


No Scneibo that is not where it started, it started with zany Zwicky FIRST theorizing Spiral Galaxies don't implode due to a counter gravitational force that exists beyond the periphery of the spiral arms, since then ONLY baryonic matter halos have been discovered where Zwicky said we'd find DM & there's a lot of gravity to be found in those baryonic halos often extending to the nearest galaxies.

Wasn't that 1933...?
Ever notice all those huge Elliptical galaxies in that Coma cluster, every one of them hundreds of times larger than our Milky Way & they contain 2/3 of the mass of the Universe, yeah a lot of mass there explaining the virial theorem.

Eliptical galaxies still present a more or less "spherical" gravitational effect...
"quasi", if you will...
Hyperfuzzy
not rated yet Nov 04, 2017
Get on board or get laughed out of your robe. Stupid search for your mistake!
Hyperfuzzy
not rated yet Nov 04, 2017
The very beginning of dark matter was the discovery in 1933 by Fritz Zwicky


No Scneibo that is not where it started, it started with zany Zwicky FIRST theorizing Spiral Galaxies don't implode due to a counter gravitational force that exists beyond the periphery of the spiral arms, since then ONLY baryonic matter halos have been discovered where Zwicky said we'd find DM & there's a lot of gravity to be found in those baryonic halos often extending to the nearest galaxies.

Wasn't that 1933...?
Ever notice all those huge Elliptical galaxies in that Coma cluster, every one of them hundreds of times larger than our Milky Way & they contain 2/3 of the mass of the Universe, yeah a lot of mass there explaining the virial theorem.

Eliptical galaxies still present a more or less "spherical" gravitational effect...
"quasi", if you will...

No questions when you read that? Just dumb acceptance?
antialias_physorg
4.8 / 5 (6) Nov 04, 2017
Anybody want to ignore the normal drudgery and answer the question in the second comment?

From the arxiv version of the paper
https://arxiv.org...0117.pdf
When the temperature is below 100 mK, the equilibrium density of 4He in the vapor phase is below 10e-12cm^3 and the number of thermal rotons in the liquid is negligible.

(Edited a bit because the numbers didn't survive the copy&paste process)
Da Schneib
5 / 5 (3) Nov 05, 2017
I can maybe fix that notation up a bit, and explain a bit more about it.

The correct notation is 10 ⁻¹² cm ⁻³. This means about 1 free evaporated helium atom per trillion cubic centimeters. This is the amount of evaporated helium expected from thermal processes at less than 100 mK temperature. The authors say this was determined in preparatory experiments intended to lead to a (so far) unrealized previous experiment called HERON intended to be used to detect solar neutrinos. To this they add their ionization idea to bring the efficiency up to the point where they can detect single helium atoms ejected from the superfluid.

[contd]
Da Schneib
5 / 5 (3) Nov 05, 2017
[contd]
Regarding residual radioactivity, because helium-4 can be rigorously purified due to the large atomic mass difference between it and its neighbors, this can be suppressed to virtually nothing (they call it "negligible" and I agree).

Regarding other sources of interfering radiation, the techniques for this are well known due to the various other dark matter particle search experiments; put it deep in a mine, surround it with detectors for ionizing radiation to eliminate cosmic rays by timing, and account for neutrino flux (this detector is so sensitive that neutrinos can also cause helium-4 nuclei to recoil, resulting in a false positive, so you have to subtract those from the observed detections).

The authors have not addressed the neutrino flux issue that I saw, but it's simple enough. There is also an issue with free helium atoms per CC per unit time, which the authors have not addressed either; the statistic they used didn't account for this.

[contd]
Da Schneib
5 / 5 (3) Nov 05, 2017
[contd]
I'd say overall that the proposal has merit, but needs further theoretical development and some further experiments to validate the technique. This isn't ready for prime time yet. But it's a great idea for looking for low-mass DM candidate particles.

An important question is, given the detection of such particles by this experiment, how were they not noticed in prior quite simple and low-energy accelerator experiments? Particles of this mass should show up as missing mass in experiments we've been doing since WWII, some sixty or seventy years. Like I said, not quite ready for prime time.
Da Schneib
5 / 5 (2) Nov 05, 2017
The very beginning of dark matter was the discovery in 1933 by Fritz Zwicky
No Scneibo that is not where it started, it started with zany Zwicky FIRST theorizing Spiral Galaxies don't implode due to a counter gravitational force
Wasn't that 1933...?
Yep. Then there's the fact noted by RNP above that Zwicky didn't deal with spiral galaxies. @Lenni's done it again, confusing Rubin with Zwicky. It seems insistent on smearing dead astrophysicists. De mortuis nil nisi bonum.

all those huge Elliptical galaxies... they contain 2/3 of the mass of the Universe, yeah a lot of mass there explaining the virial theorem.
First, they don't contain 2/3 of the mass of the universe. Second, their mass has nothing to do with the virial theorem which @Lenni obviously doesn't understand rendering it incompetent to comment. Guess they don't teach the virial theorem in nuclear technician/shit wiper courses duhhhh ummm.
Da Schneib
5 / 5 (1) Nov 05, 2017
Thanks for bringing that BS to my attention @Whyde; @Lenni does a lot of lying so I don't bother with reading what it posts much. It should go back to wiping the shit off probes at the hospital since it appears woefully unqualified to do anything that involves real physics or math.
Da Schneib
5 / 5 (5) Nov 05, 2017
And just another reminder, @Lenni:

You still haven't posted any solutions to real differential equations that actually involve GRT, specifically these:
-m'' + m'n' - m'² - 2m'/r = 0
m'' + m'² - m'n' - 2m'/r = 0
e⁻²ⁿ (1 + m'r - n'r) - 1 = 0
R₂₂ sin² ϕ = 0
Source: http://www.etsu.e...esis.pdf
And another reminder:
E² = (pc)² + (mc²)²
https://phys.org/...rgy.html
https://phys.org/...ole.html

If ya can't do the math ya can't do the physics. Simple as that. For lurkerz these are a distillation of the Shroedinger solutions to the EFE.
Hyperfuzzy
1 / 5 (1) Nov 05, 2017
And just another reminder, @Lenni:

You still haven't posted any solutions to real differential equations that actually involve GRT, specifically these:
-m'' + m'n' - m'² - 2m'/r = 0
m'' + m'² - m'n' - 2m'/r = 0
e⁻²ⁿ (1 + m'r - n'r) - 1 = 0
R₂₂ sin² Ď� = 0
Source: http://www.etsu.e...esis.pdf

If ya can't do the math ya can't do the physics. Simple as that. For lurkerz these are a distillation of the Shroedinger solutions to the EFE.

E = M c^2 is nonsense. Rationalize a quanta to an amount of mass, or more specifically a mass of charge centers. Define what motion or arrangement, don't forget your impossible mass is nonlinear.
Merrit
1 / 5 (1) Nov 06, 2017
The DM particle experiments are not a complete waste since we are ruling out the existence of particles in those ranges, but it is too much time and money in my opinion for that small gain in knowledge.

The issue I have with all particle based DM theories is that the DM to matter ratio is too constant on a galaxy by galaxy examination. I would expect much more variance. Also, the galaxies that do demonstrate higher DM ratios are all comprised of galaxies on the smaller side. While it may be the best candidate for DM that scientists can come up with, it still doesn't fit.
Zzzzzzzz
5 / 5 (2) Nov 06, 2017
Dark matter and Dark energy are just a figment of someone's imagination. Don't know what you're looking at or what's causing an "affect", may as well dream up dark stuff. What hogwash.


I guess its a waste of time asking questions or trying to find out about things.....why do those who hate science hang out on a science site? That;s a rhetorical question.... i'm not looking for an answer.....
Hyperfuzzy
not rated yet Nov 06, 2017
The DM particle experiments are not a complete waste since we are ruling out the existence of particles in those ranges, but it is too much time and money in my opinion for that small gain in knowledge.

The issue I have with all particle based DM theories is that the DM to matter ratio is too constant on a galaxy by galaxy examination. I would expect much more variance. Also, the galaxies that do demonstrate higher DM ratios are all comprised of galaxies on the smaller side. While it may be the best candidate for DM that scientists can come up with, it still doesn't fit.

If you start with something you know, instead of a theory based on nothing, expect nonsense. What you are looking for is a correct measure. The charge's field as as said before, Coulomb, Maxwell, the field extends from the center of charge to infinity. There are no particles. Multiple charges may occupy the same point, just satisfy Coulomb.
Hyperfuzzy
not rated yet Nov 06, 2017
I say this with good intentions, the nonsense response doesn't bother me, only a logical response based on fact not fiction will get my interest. So stop looking for something you think must be there 'cause you don't have a correct measure and you are using more nonsense to validate. By the way, it would invalidate the instrumentation you are using to validate. Seriously, please, think!
Hyperfuzzy
not rated yet Nov 06, 2017
Anybody want to ignore the normal drudgery and answer the question in the second comment? That was my biggest question after reading the article as well. My first guess was that based on the weight of the helium atoms they'll be able to tell the exact size/form of the particle that interacts with them, so if it's anything unusual it would stand out.

I thought I answered that. You may calculate the escape velocity from any arrangement. Note: within a very dense, and rapidly changing fields, escape is practically a given.
nikola_milovic_378
Nov 12, 2017
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nikola_milovic_378
Nov 12, 2017
This comment has been removed by a moderator.
nikola_milovic_378
Nov 12, 2017
This comment has been removed by a moderator.
nikola_milovic_378
Nov 12, 2017
This comment has been removed by a moderator.
Hyperfuzzy
1 / 5 (1) Nov 12, 2017
All bodies move around the centers of the mass of the system, from the smallest system (planet and moon) to galactic clusters. But there is also a movement about which science has no understanding. And this is a movement composed of two spins of the same size and in different directions, where the second spin rotates the body around the center of the mass of that system, according to the sinusoidal radius. If this is known, Einstein's proof of the movement of the planets and the uneven retreat of Mercury is defeated, as well as explaining why our Moon has always, one and the same side, facing the Earth. This is true for many moons around other planets.
THIS IS MY KNOW-HOW!

Wow, determining nonsense is nonsense with nonsense. Amazing!

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