XENON1T, the most sensitive detector on Earth searching for WIMP dark matter, releases its first result

May 19, 2017 by Sander Breur
XENON1T installation in the underground hall of Laboratori Nazionali del Gran Sasso. The three story building on the right houses various auxiliary systems. The cryostat containing the LXeTPC is located inside the large water tank on th left, next to the building. Credit: Roberto Corrieri and Patrick De Perio

"The best result on dark matter so far—and we just got started." This is how scientists behind XENON1T, now the most sensitive dark matter experiment world-wide, commented on their first result from a short 30-day run presented today to the scientific community.

Dark is one of the basic constituents of the universe, five times more abundant than . Several astronomical measurements have corroborated the existence of , leading to a world-wide effort to observe dark matter particle interactions with ordinary matter in extremely sensitive detectors, which would confirm its existence and shed light on its properties. However, these interactions are so feeble that they have escaped direct detection up to this point, forcing scientists to build detectors that are increasingly sensitive. The XENON Collaboration, that with the XENON100 led the field for years in the past, is now back on the frontline with the XENON1T experiment. The result from a first short 30-day run shows that this detector has a new record low radioactivity level, many orders of magnitude below surrounding materials on Earth. With a total mass of about 3200kg, XENON1T is the largest detector of this type ever built. The combination of significantly increased size with much lower background implies excellent dark matter discovery potential in the years to come.

The XENON Collaboration consists of 135 researchers from the U.S., Germany, Italy, Switzerland, Portugal, France, the Netherlands, Israel, Sweden and the United Arab Emirates. The latest detector of the XENON family has been in science operation at the LNGS underground laboratory since autumn 2016. The only things you see when visiting the underground experimental site now are a gigantic cylindrical metal tank filled with ultra-pure water to shield the detector at his center, and a three-story-tall, transparent building crowded with equipment to keep the detector running.

Scientists assembling the XENON1T time projection chamber. Credit: Enrico Sacchetti

The XENON1T central detector, a so-called liquid xenon time projection chamber (LXeTPC), is not visible. It sits within a cryostat in the middle of the water tank, fully submersed in order to shield it as much as possible from natural radioactivity in the cavern. The cryostat keeps the xenon at a temperature of -95°C without freezing the surrounding water. The mountain above the laboratory further shields the detector, preventing perturbations by cosmic rays. But shielding from the outer world is not enough since all materials on Earth contain tiny traces of natural radioactivity. Thus, extreme care was taken to find, select and process the materials of the detector to achieve the lowest possible radioactive content. Laura Baudis, professor at the University of Zürich and professor Manfred Lindner from the Max-Planck-Institute for Nuclear Physics in Heidelberg, emphasize that this allowed XENON1T to achieve record "silence," which is necessary to listen for the very weak voice of dark matter.

A particle interaction in leads to tiny flashes of light. This is what the XENON scientists are recording and studying to infer the position and the energy of the interacting particle, and whether or not it might be dark matter. The spatial information allows the researchers to select interactions occurring in the one-ton central core of the detector.

The spin-independent WIMP-nucleon cross section limits as a function of WIMP mass at 90% confidence level (black) for this run of XENON1T. In green and yellow are the 1- and 2σ sensitivity bands. Results from LUX (red), PandaX-II (brown), and XENON100 (gray) are shown for reference. Credit: Purdue University

The surrounding xenon further shields the core target from all materials that already have tiny surviving radioactive contaminants. Despite the shortness of the 30-day science run, the sensitivity of XENON1T has already overcome that of any other experiment in the field, probing unexplored dark matter territory. "WIMPs did not show up in this first search with XENON1T, but we also did not expect them so soon," says Elena Aprile, Professor at Columbia University and spokesperson for the project. "The best news is that the experiment continues to accumulate excellent data, which will allow us to test quite soon the WIMP hypothesis in a region of mass and cross-section with normal atoms as never before. A new phase in the race to detect dark matter with ultra-low background massive detectors on Earth has just began with XENON1T. We are proud to be at the forefront of the race with this amazing detector, the first of its kind."

Explore further: Green light for next-generation dark matter detector

More information: First Dark Matter Search Results from the XENON1T Experiment. arxiv.org/abs/1705.06655

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24 comments

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dirk_bruere
4.5 / 5 (8) May 19, 2017
TLDR: Nothing discovered
zorro6204
4.6 / 5 (11) May 19, 2017
So, we got nothing, but it's better nothing than before. Okay.
Lischyn
4 / 5 (9) May 19, 2017
6 paragraphs and a pretty graph with no data... title lies.
Dingbone
3.6 / 5 (10) May 19, 2017
This is fourth generation of XENON detector already - a completely useless research and futile in addition. This research is motivated with stringy and susy theories, which already failed in independent tests. The people interested in such a research should finance it from their own money. It's just void grant and salary generation scheme subsidized from money of tax payers - and another, even larger detectors are already underway. If the politicians would embezzle public money in this way, they would be already prosecuted - but everything is possible in the world of science. It also demonstrates that modern theories aren't falsifiable - if no observation is made, then the theory isn't disproved with it, but another, even more sensitive detector will be constructed instead and research continues as if nothing would ever happen. If the physicists would be so obstinate in replications of overunity, antigravity or cold fusion findings, we would have them in every kitchen already...
Dingbone
3.3 / 5 (8) May 19, 2017
michbaskett
not rated yet May 19, 2017
What sort of a reaction is hypothesized between dark matter and ordinary matter? What sort of energy levels are expected? Given mass, velocity, charge, etc, what would be the expected cascade of events showing it happened?
dnatwork
2.7 / 5 (7) May 19, 2017
They state that dark matter is five times more abundant than normal matter, as though it's a fact. Their proof is that astronomical observations have indicated it. But that's only if you interpret the astronomical data that way. Oddly, all the dark matter "halos" just happen to surround large quantities of normal matter, as in galaxy-cluster-sized masses. The only halos that are not centered on the normal mass are when the galaxy or cluster is moving at very high velocity (or is there only one of those?).

Uh, if the halos are always centered on the mass of normal matter, isn't it much simpler to say there's only normal matter, and your theory of gravity is incomplete? Especially when we know it is incomplete in the first place?

And the one instance where the halo is off-center could be that you're seeing lag in the effects; we are talking about extremely huge masses and distances here, so the lensing of distant objects behind the cluster could play out over millions of years.
Dingbone
2.3 / 5 (3) May 19, 2017
What sort of a reaction is hypothesized between dark matter and ordinary matter? What sort of energy levels are expected?
Dark matter should interact magnetically via nuclear recoil - magnetic inelastic dark matter (MiDM). The energy levels achieved are getting gradually lower as the previous detections failed and the detectors are getting increasingly sensitive. Their scintillation light produces 178 nm ultraviolet photons. To minimize the radiogenic background, the XENON1T radioassay program uses mass spectrometry techniques and high-purity germanium spectrometers that are capable of measuring radioactivity at the level of 10-6 decays per second in a kilogram of material (Bq/kg). As a comparison a typical banana has an activity of ~100 Bq/kg and it's contamination would render detector unusable.
baudrunner
2.3 / 5 (9) May 19, 2017
As I understand it, dark matter is conjecture based on ambiguous observations and bad math. The inference for its existence arises from the observation of the behavior between colossal objects extremely far away, so now they are trying to find it around here.

from: "10 Facts Everyone Should Know About Dark Matter", on the fact that we can't just see it..
It means it doesn't emit any electromagnetic radiation for all we can tell. Astronomers haven't been able to find neither light visible to the eye, nor radiation in the radio range or x-ray regime, and not at even higher energies either.
Well, that perfectly describes helium.
5. Dark matter doesn't interact much with itself or anything else.
That perfectly describes helium too.
10. But we have no direct experimental evidence.
Bingo! Just keep pumping all that money into useless experimentation.
antialias_physorg
3.7 / 5 (12) May 19, 2017
As I understand it, dark matter is conjecture based on ambiguous observations and bad math.

Well, then we can definitely conclude that you don't understand it at all.
Next.

Oddly, all the dark matter "halos" just happen to surround large quantities of normal matter, as in galaxy-cluster-sized masses.

Why 'oddly'? If it's influenced by gravity: Where else would you expect it? (More to the point - since there appears to be more dark matter than the 'ordinary' kind: Where else do you expect galaxies to be?)

isn't it much simpler to say there's only normal matter, and your theory of gravity is incomplete?

It's not simpler. It's much harder to incorporate such an explanation into the current set of theories.
Note: when you make a statement it doesn't just have to mesh with one observation. It has to mesh with ALL observations.
Starting with the simple explanations is easier than immediately jumping to the complicated ones
nrauhauser
3 / 5 (6) May 19, 2017

Starting with the simple explanations is easier than immediately jumping to the complicated ones


Is there a simple explanation for the climate change denial grade of odd comments appearing here?
Paton
2 / 5 (2) May 20, 2017
So they've made a detector and it is probably working? Result!
lengould100
5 / 5 (1) May 20, 2017
I tend to doubt that "Dark Matter" is actual massive material e.g. which interacts only via gravity. For example, the bullet cluster observation which is said to be the dramatic confirmation that DM is separate from normal matter, because in a collision of two galaxy clusters, the DM mass passed right through the collision point and moved way out past the normal matter because "it doesn't interact".

But wait a minute! That would ONLY happen if DM doesn't interact GRAVITATIONALLY with normal matter. What do they think slowed down the normal matter in the clusters, electromagnetism? No, it had to be gravity. BUT that is the only feature for which DM was invented in the first place.

I still prefer John Moffat's modified gravitation.
thingumbobesquire
5 / 5 (1) May 20, 2017
Here a WIMP, There a WIMP, Everywhere... er... Nowhere a WIMP WIMP. Maybe it's a limp WIMP...
TheGhostofOtto1923
1 / 5 (3) May 20, 2017
Yo hey. It's the hydrino. Pass it on.
http://brilliantlightpower.com
Dingbone
4 / 5 (4) May 20, 2017
@TheGhostofOtto1923 While I share your enthusiasm regarding the BrilliantLight power, I don't think that the hydrinos are responsible for it. If their formation would release so much of energy, then the hydrino would be way more frequent in the universe and representing substantial portion of stars and large planets, because it would be also difficult to decompose. Other than that, the WIMPs woulds share many aspects of behavior with hydrinos (mass, zero charge, etc..), if they would exist both.
TheGhostofOtto1923
3 / 5 (2) May 20, 2017
@TheGhostofOtto1923 While I share your enthusiasm regarding the BrilliantLight power, I don't think that the hydrinos are responsible for it. If their formation would release so much of energy, then the hydrino would be way more frequent in the universe and representing substantial portion of stars and large planets, because it would be also difficult to decompose. Other than that, the WIMPs woulds share many aspects of behavior with hydrinos (mass, zero charge, etc..), if they would exist both.
Well as you might suspect Dr Mills has thorough explanations for your doubts which I'm certainly not going to try to repeat them here.

But I suspect you haven't chosen to search them out yourself but rather assume you can naturally out-think him without having to check?

That's the way it appears at any rate.
arcmetal
3 / 5 (2) May 20, 2017
As I understand it, dark matter is conjecture based on ambiguous observations and bad math. ...


I would appear its due to bad math.

I had already posted a possible explanation for galactic rotations by simply using Newton's equations, and therefore no need to summon any dark matter. It was originally posted by Nanobanano back in 2011:

https://phys.org/...ton.html

xponen
5 / 5 (1) May 20, 2017
What is the "faint annual variation" that they detect in previous detector? The DAMA/LIBRA project claim it was dark matter in 1998, but the previous project (XENON100) ruled it out. So, what is the annual variation?
eljo
3 / 5 (4) May 21, 2017
Why don't they just read up about all the pieces of evidence for electricity as the main agent for all the effects they purport to find with dark matter. This Dark matter business is too sad to watch. Dark matter researchers clearly are unaware of the details and explicative power of the alternatives. They must read up about it and come to understand that scale invariant electric phenomena and currents exist in space. Electromagnetic force is responsible for gravitational effects and it is a far more elegant theory able to explain all observed phenomena in great detail, without having to resort to the complex theoretical house of cards that dark matter hypothesis is.
Dingbone
2.6 / 5 (5) May 21, 2017
Dark matter researchers clearly are unaware of the details and explicative power of the alternatives
They're of course aware of it, but they would lose their job immediately if they would admit it. You cannot research and publish axions if you're working in underground detectors of WIMPs and vice-versa. And without publications you cannot work anywhere in science for full salary. The free thinking today remains dedicated to people, who aren't doing it as a their main job. And being good in something today requires to do it as a main job.
Dingbone
2.3 / 5 (3) May 21, 2017
The Physicist Who Denies Dark Matter - he was ignored many years, because physicists hoped to make grants and glory with WIMPs and another particles of dark matter - but their attempts all failed. So that they finally take Mordehai Milgrom more seriously.
bschott
not rated yet 11 hours ago
Well as you might suspect Dr Mills has thorough explanations for your doubts which I'm certainly not going to try to repeat them here.

Dr. Mills and the Brilliant light team are in need of retirement funds, hence the "news" coverage on CNN about how the breakthrough is here, and the over unity device that functions because of Hydrino physics is just around the corner...they have been navigating that corner for quite some time now. That the team would actually claim it (the hydrino) is DM shows the credibility of everything else they claim.
Merrit
not rated yet 6 hours ago
Well I hope they continue to fail to create an over unity device considering any over unity reaction could lead to the utter destruction of the entire universe.

E = MC^2 over unity = infinite energy = bye bye everyone. Think of a nuclear reaction with unlimited nuclear material.

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