> it’s far too early to claim a discovery, physicists warn...“How do you even make sense of one event?” muses Tom Shutt, a particle astrophysicist at SLAC National Accelerator Laboratory and co-founder of the LZ project. “We just decided we should publish and think really, really, really hard about what that event could be.”
Very hard to manage jumping the gun by reporters. Sounds like they saw some new data. No idea what it is.
I read their preprint[1] and they did a thorough job. They investigated a number of the things I'd suspect if I were looking for mis-reconstructed events or weird backgrounds.
So it's certainly interesting!
That said, particle physics history is full of 3 sigma particle "discoveries" that disappeared with more data. They're collecting more, so hopefully we'll learn more in a few more years.
In one sense anything that passed all their background rejection is a WIMP. To interact with a nucleus through so much matter, it's not interacting electromagnetically. The main candidate for a strong force interaction would be a neutron, and they did a lot of work to model that and eliminate it as a background. So definitionally it would be a WIMP.
They were pretty model agnostic in what they were looking for. They modeled and simulated a number of different ways a WIMP could interact with normal matter. If this is a discovery, more data will be needed to figure out the nature of that interaction and how it fits into particle physics.
But there's always a chance it's something completely new, or some extremely rare manifestation of things we already know about, but have never seen before. And even if it is WIMP, it may not be the right type of WIMP (wrong mass, or wrong interaction strength) to explain cosmological dark matter.
The detector from which data is taken to do this analysis contains 7 tons of liquid xenon. It is inside of a larger detector, which contains hundreds of tons of water and more than 10 tons of a scintillator. One of the functions of that outer detector is to absorb neutrons and other infiltrates coming from the rock.
When doing this kind of thing, the analysts will plot the rate of events as a function of "distance from the outer surface" and confirm that it decreases, and in this case "is 0" inside of the detector used for analysis.
But keep in mind that all statements are made statistically, so it's not that the event _can't_ be an external neutron, but that it is _very_ unlikely to be.
They have a lot of shielding for the detector, and also if there were a significant source of neutrons they'd expect to see other evidence, both in the detector and in the separate "veto" detector that surrounds the main detector.
That's not to say it can't be a neutron, but it would be surprising if it were.
This sort of thing is really useful for helping people to understand what the purpose of scientific publication is. It's not about presenting finished products to society, it's more like a Discord where you communicate new findings with other authors. Often the reason for a communication is because you found something weird, and you want other people to know about it so they can help you confirm or rule it out as bad data. People shouldn't feel gunshy about this. (My field even has a conference for failed results, CFAIL.) I like to highlight examples of this stuff, because I see so many angry online comments when a paper turns out to be "wrong" or doesn't replicate.
Yep. Publishing like this gives a heads up to those operating similar observatories to keep an eye out for similar events. And it gives a nudge to theorists that might help them start looking in a more fruitful direction, appropriately caveated that it may be a statistical fluke.
The mainstream TV news report that I saw about this ended with a comment about how we should continue to fund this detector. Made me wonder if the nature of this release involved forces other than purely scientific ones. Apparently funding has already been cut for the successor to the LUX-ZEPLIN detector.
Particle physics is not a particularly large community. There is a hand-countable number of experiments like this, and the folks working on each of them know the folks working on each of the others. The collaborations executing each experiment are comprised of scientists employed by multiple independent institutions, both public and private, typically across national borders. Internally, the collaborations have a democratic structure with individual researchers acting as institutional representatives serving in what is essentially a parliamentary structure to make decisions. The software to determine results is always public within the collaboration and reviewed well in advance of making any truly public disclosure like this.
Culturally, an attempt to intentionally distort or misrepresent data to suggest a result like this would not be tolerated. You can imagine a bad actor writing a single-author paper with fakery, but a collaboration at this level is inherently critical of itself and everyone holds each other accountable.
But mistakes do happen. Exciting results or hints of exciting results can appear due to well-intentioned researchers making convenient mistakes which get glossed over for psychological reasons and then add up to appear as something significant. You can read about "blinding" (which is mentioned in the paper) to get a feel for the techniques researchers employ to not only guard against fabricating results intentionally, but even unintentionally.
The small pool also lends itself to a lack of unbiased reviewers. If everyone in the community is more-or-less tied to the research, who can best objectively test it, from a blinded POV?
That is a great point. I'm not sure if I fully understand your question, but I'll comment on both "testing," meaning doing the analysis, and "reviewing," meaning peer review.
The point of "blinding," as I mentioned it before, is to guard against biasing the result due to choices made by analysts while figuring out how to compute their final answer. Part of that is just psychological --- if an analyst _knows_ that the data is obscured, for lack of a better term, in a way such that they can't believe a signal that they see (for example --- that's just one way to blind), then they won't feel any emotion or excitement about things they encounter while constructing the analysis, because they know what they're looking at isn't real, and that helps them to maintain objectivity. It's also common to have multiple independent analysis teams for something like this --- they know that they'll have embarrassed themselves if they don't all get the same result both before and after unblinding, which provides pressure to maintain objectivity.
As far as review goes --- there are physicists who believe in dark matter, and there are physicists who don't believe in dark matter. But all particle physicists and nuclear physicists use the same core technical and statistical methods. For a result like this, there will be a few "core analysts" who do the analysis, typically graduate students and postdocs. Their advisors review their work, through the lens of making sure that they are doing so sanely. The collaboration will also establish an internal review committee to comb through the documentation and software which produced the result, not necessarily trying to disprove what they found, but really looking at it critically. Once it gets to a journal, they'll get reviewers who may be biased for or against the result, and who may or may not work directly on dark matter detection, but who can all assess the methodology by which the result was obtained. That's probably the best we can do with humans involved.
I'm not suggesting distortion or misrepresentation of the published result. The actual preprint is quite clear on the nature and limitations of the result, and there's no reason to think that what they're reporting didn't happen as described.
However, the context here is that the DOE has already paused funding for the experiment's successor, XLZD, for an unspecified amount of time which realistically, is probably going to depend on the next US presidential election. At the same time, the DOE encouraged the LZ project to develop scenarios for continuing to operating beyond its current end date of 2028.
Now, here's what the NBC Bay Area report I mentioned[0] ended with:
> "All the more reason, they say, to keep these machines running. [...] They'd like to keep the machines running, they wanna keep doing this research, they're applying for funding now, so fingers crossed, we'll have more updates on this [...]"
The media attention this received was not the organic result of some journalist noticing the preprint or the talk at TeVPA in Japan. There was a major wave of synchronized official press releases, coinciding with the TeVPA talk, from Berkeley National Lab[1], Brown University[2], SLAC[3], Brookhaven[4], Stanford[5], University of Sydney[6], and others including UMass Amherst and Imperial College London.
Now, these institutions are all involved in the collaboration somehow, so it makes sense that they would coordinate press releases for a major result. The question is whether this result warrants such treatment. It's a single event at 2.6 sigma global significance. Promoting it in this way was a choice, and I'm pointing out that it seems quite possible - in fact I'd say extremely likely - that that choice was made with the funding situation top of mind.
Thanks for clarifying, and my apologies if I came off as argumentative --- what you _are_ suggesting makes sense and is a reasonable thing to wonder about.
But I don't see anything particularly strange or coordinated is happening. From the collaboration's perspective, it's quite stressful having this event. They've already unblinded, so it would be unethical to do anything other than report what they found. If they publicize it and it's a mistake, then that's a big blow to their credibility. But if they withhold it and it's real, then they miss making the discovery and/or bias their future analyses on larger datasets without disclosing that to the community. So they are in a tough spot, and are safest to just tell the world what they saw.
This is getting media attention because it would be a big deal to the general public if this ends up being a real. Someone in the field wouldn't claim that it's real, but the possibility is catnip to folks looking for a sensational headline. That the press releases are synchronized in time is because the result was just released right now and they're all doing their commentaries right away --- for something like this, each institution independently negotiates a release with the local researchers who are involved. They all promise to wait until the result is officially released, out of respect for the scientific process, like you say, but the different institutions aren't coordinating with each other. They're just all respecting their own researchers.
Is a 2 or 3 sigma fluctuation worth a lot of press? Personally, I don't think so. But we don't know if it's a fluctuation yet, and no institution is going to pass on having made it clear, if this does turn out to be real, that they were involved.
All that being said: I would very much like these folks to continue to receive funding. They are professional and do excellent work, as demonstrated here.
> They've already unblinded, so it would be unethical to do anything other than report what they found.
Absolute and utter ridiculous nonsense. Can you not just admit when you're wrong?
It's perfectly ethical for them to give a talk at TeVPA about a paper they've published.
But at least 8 global, coordinated press releases? That's a choice, with consequences.
And one of those consequences is that they reveal themselves as chasing funding above all else. Scientific rigor goes out the window. 2.6 sigma results become amazing new discoveries.
It's not really their fault - it's systemic. But don't try to pretend that this is somehow the normal process of science being conducted with integrity.
> That said, particle physics history is full of 3 sigma particle "discoveries" that disappeared with more data. They're collecting more, so hopefully we'll learn more in a few more years.
More than one would expect? Like having an IQ of 140 or more? ;)
> That said, particle physics history is full of 3 sigma particle "discoveries" that disappeared with more data.
The idea is that because 3 sigma means a ~1/1000 chance of the thing being explained by random chance, 1 in 1000 experiments will produce a bogus 3 sigma result, and we do many thousands of experiments.
and also because a result always has the caveats of "if we did our experimental design and math right". A 1/1000 rate of experimental/code design errors will double the number of incorrect 3 sigma results.
Not well informed on the topic- but the title made me think of the recently launched Roman Space Telescope.
The difference: LUX-ZEPLIN, which is underground, is waiting to detect a dark matter particle itself. On the other hand, NGRST seeks to observe the effects of dark matter.
> If the new result is real, more signals should emerge soon. LZ researchers have already collected three times as much data as they used in the paper.
It sounds like this implies they've seen 3x more events but it seems like they would have said that if it were the case. Have they just gathered more data about the single event or is this 4 separate events they're talking about?
If this anything like CERN detectors, they get amounts of data so vast that they have to discard almost all of it to be even able to record it. Depending on heurestics you use to discard data you might be discarding what you are looking for and after adjustment will get some new interesting events, but still actually processing the candidates might take a long time.
This raises what is (I think) an interesting question. CERN is a collider, so they are _trying_ to produce lots of stuff, and they do (lots and lots of stuff). They can't write it all to disk, and most of it isn't interesting enough to try.
The work being done here falls into the category of "low background physics" --- they aren't trying to produce anything, and actually put quite a bit of effort into doing the opposite, by removing all sources of particles (e.g. sourcing materials free of radioactive contaminants, physically cleaning all surfaces and purifying all fluids involved, etc).
So the detector, if built properly, is fairly quiet, and you try to write as much data to disk as you can (e.g., if something even fairly-potentially interesting happens, you save it). Then when you analyze the data like this, you ignore the majority of what you've got --- only a teeny fraction makes it into an analysis of this caliber.
Detectors like this work on exposure. They're always on (except for calibration and maintenance), waiting for events to happen. This paper was written with 2.8 tonne-years of data. That is, 4.7 tonnes of liquid xenon for a little mmore than half a year. The detector has 7 tonnes, and the 4.7 number reflects cuts they made on parts of the detector that either they don't understand as well, or have higher backgrounds.
As they better understand the detector, they can use more of that mass. They have data from it, but they just didn't use it. And they're always collecting more data, too, as time passes.
So the 3x is saying they have something like 8.5 tonne-years of data.
So they have 7 tonnes of Xenon. Events detected all around in the matter, but the PMTs can localise where the event happened. So they can virtually segment parts of the detector where they are sure all the outside effects are understood and taken care of.
They collected x3 more hay, and they still have to processes it and try to find any needle mixed with it.
Hopefully it the new data may have 3 additional events, or perhaps 2 or perhaps 4 or perhaps 10 or perhaps... Or the reported event may be false event caused by a lucky coincidence, and they may find 0 additional events.
At some level, it could be (and that would be an great discovery as well!). It's a question of probabilities: it's unlikely to be any of the things that we already know about, but that doesn't mean that it's something new. Unlikely things happen --- infrequently. As stressed in the article and elsewhere in comments, more data should elucidate what is going on. That's the difficulty of these kinds of searches: there is one event, and we can't make clear, confident statements about one event.
Based on my very amateurish skim of this and a related paper, maybe so? They simulated the neutrino background as solar and cosmic ray atmospheric sources, so any source with a different energy distribution is perhaps a possible explanation for the event, I think.
But probably more likely is for this to have been a particularly energetic event in the tail of one of the known sources of neutron recoil detection they did model. More events needed!
I actually saw one of the authors present the data yesterday, one of the audience comments was indeed that this could be explained by an astrophysical neutrino striking the detector (all other neutrino sources have energy thresholds much lower than the detected data), but the data on astrophysical neutrinos is sparse (in part why detectors like IceCube exist), so I believe the argument is that the chances that an astrophysical neutrino would strike the detector is negligible.
I think the WIMP interaction process via the models they tested and the data on astrophysical neutrinos from other detectors gives at least several(?) orders of magnitude of separation in the rate at which each would strike the detector. Of course this would not fully rule out the possibility that it is a stray neutrino.
I think it's cool that there's still unconfirmed hypothesizes, and still unexplained phenomena in the science that's investigating these hypothesizes.
I hope this turns into a real discovery about something; but even if it's an equipment malfunction, hopefully it's a lesson that can be turned into improving the detector.
The moment there are no more unconfirmed hypotheses you can assume something is wrong with sciences. All provable models (theories, explanations) that we have, or could have, are by definition wrong or incomplete.
I'm guessing you're alluding to Goedel's I completeness theorem, but that really doesn't apply to physics. It's a statement about certain properties of formal systems - basically it tells us that for any formal system that's at least as powerful as arithmetic, it's impossible to prove every statement that is true in that system.
This doesn't in any way mean that you can't in principle describe with perfect accuracy with such a statement, in a provable way, every aspect of physics. Sure, you might need a theorem that can't be proved and be stuck because of that, but it's not a given. Physics certainly doesn't depend on all possible statements in that formal system to accurately model the real world, and so Goedel's theorem can't prove that the subset that physics needs might not be all probable.
I don't think Gödel is necessarily what is meant here, there are very good information theoretical(and other) reasons you can never describe a system with truly perfect accuracy. The map has to be become the territory for genuinely perfect accuracy.
> Such behavior could require dark matter to be more complicated than just a single new type of particle. For example, the dark matter particle might have some internal structure, like an ordinary atom, so it would only interact if hit hard enough to excite it to a higher energy internal state
I get a little shiver imagining that the dark matter might be something like ordinary atoms. Imagine that other 85% of the universe could have its own parallel atomic table, chemistry, even some kind of life utterly alien to us?
It's possible that there could be an entirely different charge mechanism that works exactly like ours but they don't interact at all; but the whole premise of dark matter is that it doesn't seem to have any self-interaction outside of gravity.
The premise of dark matter is that it is something with gravity that does not otherwise interact with any of our detectors (e.g. "normal" matter); or that any such interactions are weak enough that it is plausible we have not noticed.
By itself, that does not exclude the possibility of dark matter having other interactions which do not interfere with our detectors.
I guess so. If you could sort of measure the dark matter distribution, there might be a structure under it, but strictly speaking isn’t it limited to saying it’s not at least likely to emit light but does have mass.
But it does bound it: if dark matter has self-interactions then the apparent distribution would be different. Regular matter forms stars and galaxies and all the structures we see because it can self-interact.
Since where we see dark matter mass shadows we don't see structure formation, what self interaction it may have must be very, very limited.
That doesn't rule out "dark matter having other interactions which do not interfere with our detectors" Dark sector theories which include other dark particles or new particle interactions are not controversial amongst cosmologists in this space. For example there's a whole area of study around "dark photons" which would mix with our photons and interact with dark matter.
It's very hard to explain the gravitational halo around the galaxies if your dark matter can interact with itself. If it interacted like normal matter, it would have a distribution similar to the gases, and not spread way into intergalactic space.
"Imagine a universe, like ours, overlapping ours, except where some of its matter spontaneously rips itself apart, and other matter can be mashed together if you squeeze it hard enough." "That's nightmare fuel! Fortunately it's probably impossible, so far as we can tell."
I can imagine other scary thoughts, though. Ever read any Warhammer lore?
On this the same line of thoughts, so far we have 0 proof that all dark matter is _the same_. We observe gravity effects but IIRC they very little tell us about their own homogeneity. We very well could have a few parallel sectors, one of which is ours.
Maybe there are even dark scientists trying to explain the missing 15% of the universe! One such scientist, easily pegged as a kook, suggests a model with SU(3) x SU(2) x U(1) gauge symmetry, with one sector spontaneously broken by a scalar field, and three flavors of fermions to allow for enough CP violation and masses spanning 10 or 11 orders of magnitude.
i have zero knowledge of physics, but I just can't believe something like dark matter exists. My intuition is that some math just isn't correct and falls apart at the scales of the observable universe. No idea what equations are used for getting to the reslut of having 85% unexplained matter in the universe, but I really assume there's just a constant missing or our math in general just inaccurate or not considering specific effects.
I'm not a physicist either, but the amount of evidence pointing in the direction of dark matter is extremely significant, it's a little silly to just dismiss all that based on your intuition.
For those who are interested in learning why physicists think dark matter exists, there's an excellent and accessible talk[1] freely available over at PIRSA where an astrophysicist goes through exactly what we know about the universe and how many different kinds of evidence all seem to point in a similar direction: dark matter exists.
> I just can't believe something like dark matter exists.
It takes only a small amount of knowledge of physics to understand why and how dark matter might be possible, even likely. So small, in fact, that I can describe it in this comment.
The tl;dr is that all the senses you experience - sight, touch, smell, taste, and hearing - depend on the electromagnetic (EM) interaction. Touch, smell, taste, and hearing all depend on how electrons interact, and sight depends on how photons interact with electrons. But EM is only one of four fundamental interactions that we know of. We humans are essentially blind to all the others, without using devices to detect their presence.
But using devices we've invented, we can detect all sorts of things that we can't detect directly with our senses. X-rays and gamma rays, for example. But those are still just high-energy photons, not a different kind of particle altogether. They just help illustrate how limited our senses are.
A better example is the neutrino. They're pretty close to being "dark matter," because they don't interact via electromagnetism. As a result, they can pass right through your body, because there's nothing much to stop them. You're just as invisible to a neutrino as a neutrino is to you. It's estimated that about 100 trillion neutrinos pass through your body each second.
But neutrinos aren't perfectly "dark" - although they don't interact with electromagnetism, they do interact via the weak nuclear interaction, which is mostly something that happens inside the nuclei of atoms. (They also interact via gravity, but they have very small mass, so that doesn't help us detect them.)
We can detect neutrinos by building huge tanks full of very pure substances like water or argon, and burying them deep underground, to shield them from other interference. We can then look for the tell-tale signs that occur when a neutrino just happens to have a direct hit on an atomic nucleus, something that doesn't happen very often because nuclei are very small. That's why we need large tanks - to increase the odds of a hit.
The IceCube neutrino detector in Antarctica (https://icecube.wisc.edu/science/icecube/) extends to 2.5 km underground, and Super-Kamiokande in Japan (https://www-sk.icrr.u-tokyo.ac.jp/en/sk/) is buried 1 km below a mountain. They're able to detect neutrinos with high confidence, because aside from the tell-tale sing we can often even relate the neutrinos they detect to astronomical sources such as supernovae and supermassive black holes.
Neutrinos show that it's possible to have matter that doesn't interact via electromagnetism, which is all but invisible to us. And not just invisible - it can pass right through us. In the case of neutrinos, we're just "lucky" that they participate in the weak nuclear interaction, so we can detect them if we try hard enough. But what if a particle didn't do that? Then you'd have real dark matter - particles that we can't detect at all, except via the energy they carry, which participates in the gravitational interaction. But it's very difficult to detect tiny particles using gravity - which is why the first place we think we've detected dark matter is at large scales, in the motion of galaxies, where the collective mass of dark matter is large enough to be detected.
With all this in mind, a question dark matter skeptics would need to answer is, why wouldn't we expect dark matter to exist? We've identified quite a large zoo of particles, and what distinguishes each of them is that they each participate differently in the different interactions that we know about. Here's a little table to illustrate that:
>it could just have a very small degree of interaction that we can't easily detect, which is what the OP experiment is counting on.
It's an open question, right, whether dark matter has no interaction or just very little interaction with normal matter? If there's none, this experiment will detect nothing but noise.
I'm confused why, if dark matter exists and has mass (since it interacts gravitationally), there's no noticeable missing results from high-energy events that create particles. Shouldn't dark matter particles be generated by, say, cosmic ray collisions? Or black hole decay?
> It's an open question, right, whether dark matter has no interaction or just very little interaction with normal matter? If there's none, this experiment will detect nothing but noise.
Correct. What this experiment (LUX-ZEPLIN) is looking for is the effects of xenon nuclei being "bumped" - recoiling - due to something undetectable. It doesn't matter what interaction mediates the recoil - it could even be a so-far-undiscovered interaction. They're just looking for evidence of the recoil happening. But if the only interaction is gravity, they won't detect anything, since gravity is too weak for us to detect the effects of at that scale.
> I'm confused why, if dark matter exists and has mass (since it interacts gravitationally), there's no noticeable missing results from high-energy events that create particles.
Particle physicists actively look for this, e.g. in reactions in particle accelerators. But not finding evidence of that only places constraints on how strongly dark matter can couple to ordinary matter, it doesn't rule it out.
> Shouldn't dark matter particles be generated by, say, cosmic ray collisions?
Not necessarily. Just being energetic doesn't guarantee anything. There's a bit of a chicken-and-egg issue here: without knowing more about dark matter, we can't predict what reactions might produce it. That's why experiments like LUX-ZEPLIN make as few assumptions as possible - all it requires is that some mechanism for energy transfer from dark matter to matter exists.
> Or black hole decay?
Black hole decay has never been observed. Since it's purely theoretical, no matter how well-justified it is, it doesn't really help in the search for dark matter. There's no reason that Hawking radiation couldn't include dark matter, in fact if dark matter exists it probably would, but we have no way to detect that.
Even if say black hole collisions (which have been indirectly observed) produced dark matter, we wouldn't really have any way of detecting it at the distances in question.
Maybe you shouldn't give much credence to your intuitions if you don't really know much about the subject. Obviously experts have those simple intuitions too except they also know the details of the theories underlying it all so they can form informed opinions.
Here's a serious question: If you start with "I don't know anything about what I'm going to talk about...", why even post?
I wouldn't go into a neurological medical thread, and post "I'd guess it doesn't even exist" as a solution for Alzheimer's. But you just did the same, analogously.
I never understood why people cite this as a demonstration for how little we humans understand about our world.
The reason we haven't mapped the seafloor is because why would we? It's like arguing we know nothing about biology because we've only sequenced the genome of a fraction of humans or something. It's not that we can't do it, the reason we haven't done it is because there's no good compelling reason to do it. What do we expect to learn from mapping 100% of the sea floor?
As for the parents question – "How many years until we've discovered "everything"?"
I think we may be fairly close to knowing everything we can know and it's quite reasonable to assume we're now comfortably on the tail end of the S-curve of physics discoveries. I hope I'm wrong of course.
I cite it because we're barely scratching the surface of our own world, which is one of a potentially infinite number of worlds that is encapsulated by the word "everything."
Why would we map the seafloor is an insane question that immediately invalidates all other opinions that you may have, unfortunately. The human embodiment of that meme with the pickaxe guy walking away from a diamond strike if only he had swung once more.
It's so hubristic to assume that our generation is the one that will discover the answers to everything.
> I cite it because we're barely scratching the surface of our own world, which is one of a potentially infinite number of worlds that is encapsulated by the word "everything."
I think maybe I was assuming the parent was referring specifically to physics discoveries while you were assuming that they were asking more broadly about how many years until we've discovered everything discoverable?
Unless you are actually arguing there's likely lots of physics discoveries to be made because humans have only photographed a fraction of trees on the earth, or mapped a fraction of the seafloor, or sequenced only a fraction of the genomes of known species.
>> or the far bigger next version of the PandaX detector, currently under development in China...
Has there ever been an article about particle physics that didnt end with a statement about the "next and bigger" version of the current detector. The field has an addiction. No matter the size/luminocity, they will only ever crave a bigger hit.
One wonders if we should measure detectors as we do nuclear bombs: by the kiloton mass of thier detection medium. The DUNE detector would be a 70 kiloton-class detector. Super-Kamiokande, 50kt.
I'm out of touch and 5 years old, so please someone explain to me, but I thought the galaxies were bound together by divets in spacetime based on their mass dictated by the Higgs field. Now its dark matter binding the galaxies together?
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[ 0.26 ms ] story [ 3.7 ms ] threadVery hard to manage jumping the gun by reporters. Sounds like they saw some new data. No idea what it is.
Looking forward to the follow up.
Writers: Is the heat death of the universe coming?
So it's certainly interesting!
That said, particle physics history is full of 3 sigma particle "discoveries" that disappeared with more data. They're collecting more, so hopefully we'll learn more in a few more years.
[1] https://lz.lbl.gov/wp-content/uploads/sites/6/2026/08/LZ_Pre...
They were pretty model agnostic in what they were looking for. They modeled and simulated a number of different ways a WIMP could interact with normal matter. If this is a discovery, more data will be needed to figure out the nature of that interaction and how it fits into particle physics.
But there's always a chance it's something completely new, or some extremely rare manifestation of things we already know about, but have never seen before. And even if it is WIMP, it may not be the right type of WIMP (wrong mass, or wrong interaction strength) to explain cosmological dark matter.
When doing this kind of thing, the analysts will plot the rate of events as a function of "distance from the outer surface" and confirm that it decreases, and in this case "is 0" inside of the detector used for analysis.
But keep in mind that all statements are made statistically, so it's not that the event _can't_ be an external neutron, but that it is _very_ unlikely to be.
That's not to say it can't be a neutron, but it would be surprising if it were.
Culturally, an attempt to intentionally distort or misrepresent data to suggest a result like this would not be tolerated. You can imagine a bad actor writing a single-author paper with fakery, but a collaboration at this level is inherently critical of itself and everyone holds each other accountable.
But mistakes do happen. Exciting results or hints of exciting results can appear due to well-intentioned researchers making convenient mistakes which get glossed over for psychological reasons and then add up to appear as something significant. You can read about "blinding" (which is mentioned in the paper) to get a feel for the techniques researchers employ to not only guard against fabricating results intentionally, but even unintentionally.
The point of "blinding," as I mentioned it before, is to guard against biasing the result due to choices made by analysts while figuring out how to compute their final answer. Part of that is just psychological --- if an analyst _knows_ that the data is obscured, for lack of a better term, in a way such that they can't believe a signal that they see (for example --- that's just one way to blind), then they won't feel any emotion or excitement about things they encounter while constructing the analysis, because they know what they're looking at isn't real, and that helps them to maintain objectivity. It's also common to have multiple independent analysis teams for something like this --- they know that they'll have embarrassed themselves if they don't all get the same result both before and after unblinding, which provides pressure to maintain objectivity.
As far as review goes --- there are physicists who believe in dark matter, and there are physicists who don't believe in dark matter. But all particle physicists and nuclear physicists use the same core technical and statistical methods. For a result like this, there will be a few "core analysts" who do the analysis, typically graduate students and postdocs. Their advisors review their work, through the lens of making sure that they are doing so sanely. The collaboration will also establish an internal review committee to comb through the documentation and software which produced the result, not necessarily trying to disprove what they found, but really looking at it critically. Once it gets to a journal, they'll get reviewers who may be biased for or against the result, and who may or may not work directly on dark matter detection, but who can all assess the methodology by which the result was obtained. That's probably the best we can do with humans involved.
However, the context here is that the DOE has already paused funding for the experiment's successor, XLZD, for an unspecified amount of time which realistically, is probably going to depend on the next US presidential election. At the same time, the DOE encouraged the LZ project to develop scenarios for continuing to operating beyond its current end date of 2028.
Now, here's what the NBC Bay Area report I mentioned[0] ended with:
> "All the more reason, they say, to keep these machines running. [...] They'd like to keep the machines running, they wanna keep doing this research, they're applying for funding now, so fingers crossed, we'll have more updates on this [...]"
The media attention this received was not the organic result of some journalist noticing the preprint or the talk at TeVPA in Japan. There was a major wave of synchronized official press releases, coinciding with the TeVPA talk, from Berkeley National Lab[1], Brown University[2], SLAC[3], Brookhaven[4], Stanford[5], University of Sydney[6], and others including UMass Amherst and Imperial College London.
Now, these institutions are all involved in the collaboration somehow, so it makes sense that they would coordinate press releases for a major result. The question is whether this result warrants such treatment. It's a single event at 2.6 sigma global significance. Promoting it in this way was a choice, and I'm pointing out that it seems quite possible - in fact I'd say extremely likely - that that choice was made with the funding situation top of mind.
[0] https://www.youtube.com/watch?v=bf3aW0xTEEc
[1] https://newscenter.lbl.gov/2026/09/01/lz-sees-surprising-res...
[2] https://www.brown.edu/news/2026-09-01/lz-dark-matter-results
[3] https://www6.slac.stanford.edu/news/2026-09-01-lz-sees-surpr...
[4] https://www.bnl.gov/newsroom/news.php?a=123133
[5] https://news.stanford.edu/stories/2026/09/dark-matter-detect...
[6] https://www.sydney.edu.au/news-opinion/news/2026/09/03/lz-ex...
But I don't see anything particularly strange or coordinated is happening. From the collaboration's perspective, it's quite stressful having this event. They've already unblinded, so it would be unethical to do anything other than report what they found. If they publicize it and it's a mistake, then that's a big blow to their credibility. But if they withhold it and it's real, then they miss making the discovery and/or bias their future analyses on larger datasets without disclosing that to the community. So they are in a tough spot, and are safest to just tell the world what they saw.
This is getting media attention because it would be a big deal to the general public if this ends up being a real. Someone in the field wouldn't claim that it's real, but the possibility is catnip to folks looking for a sensational headline. That the press releases are synchronized in time is because the result was just released right now and they're all doing their commentaries right away --- for something like this, each institution independently negotiates a release with the local researchers who are involved. They all promise to wait until the result is officially released, out of respect for the scientific process, like you say, but the different institutions aren't coordinating with each other. They're just all respecting their own researchers.
Is a 2 or 3 sigma fluctuation worth a lot of press? Personally, I don't think so. But we don't know if it's a fluctuation yet, and no institution is going to pass on having made it clear, if this does turn out to be real, that they were involved.
All that being said: I would very much like these folks to continue to receive funding. They are professional and do excellent work, as demonstrated here.
Absolute and utter ridiculous nonsense. Can you not just admit when you're wrong?
It's perfectly ethical for them to give a talk at TeVPA about a paper they've published.
But at least 8 global, coordinated press releases? That's a choice, with consequences.
And one of those consequences is that they reveal themselves as chasing funding above all else. Scientific rigor goes out the window. 2.6 sigma results become amazing new discoveries.
It's not really their fault - it's systemic. But don't try to pretend that this is somehow the normal process of science being conducted with integrity.
More than one would expect? Like having an IQ of 140 or more? ;)
The idea is that because 3 sigma means a ~1/1000 chance of the thing being explained by random chance, 1 in 1000 experiments will produce a bogus 3 sigma result, and we do many thousands of experiments.
The difference: LUX-ZEPLIN, which is underground, is waiting to detect a dark matter particle itself. On the other hand, NGRST seeks to observe the effects of dark matter.
It sounds like this implies they've seen 3x more events but it seems like they would have said that if it were the case. Have they just gathered more data about the single event or is this 4 separate events they're talking about?
The work being done here falls into the category of "low background physics" --- they aren't trying to produce anything, and actually put quite a bit of effort into doing the opposite, by removing all sources of particles (e.g. sourcing materials free of radioactive contaminants, physically cleaning all surfaces and purifying all fluids involved, etc).
So the detector, if built properly, is fairly quiet, and you try to write as much data to disk as you can (e.g., if something even fairly-potentially interesting happens, you save it). Then when you analyze the data like this, you ignore the majority of what you've got --- only a teeny fraction makes it into an analysis of this caliber.
As they better understand the detector, they can use more of that mass. They have data from it, but they just didn't use it. And they're always collecting more data, too, as time passes.
So the 3x is saying they have something like 8.5 tonne-years of data.
Hopefully it the new data may have 3 additional events, or perhaps 2 or perhaps 4 or perhaps 10 or perhaps... Or the reported event may be false event caused by a lucky coincidence, and they may find 0 additional events.
But probably more likely is for this to have been a particularly energetic event in the tail of one of the known sources of neutron recoil detection they did model. More events needed!
Glad to see such things getting re-purposed instead of just sealed off and abandoned.
I hope this turns into a real discovery about something; but even if it's an equipment malfunction, hopefully it's a lesson that can be turned into improving the detector.
Especially after JWT started looking deeper into the early universe.
This doesn't in any way mean that you can't in principle describe with perfect accuracy with such a statement, in a provable way, every aspect of physics. Sure, you might need a theorem that can't be proved and be stuck because of that, but it's not a given. Physics certainly doesn't depend on all possible statements in that formal system to accurately model the real world, and so Goedel's theorem can't prove that the subset that physics needs might not be all probable.
Why couldn't the territory be losslessly compressible?
I get a little shiver imagining that the dark matter might be something like ordinary atoms. Imagine that other 85% of the universe could have its own parallel atomic table, chemistry, even some kind of life utterly alien to us?
By itself, that does not exclude the possibility of dark matter having other interactions which do not interfere with our detectors.
Since where we see dark matter mass shadows we don't see structure formation, what self interaction it may have must be very, very limited.
Don’t ask me how or why, but this is essentially the universal (pun intended) consensus amongst cosmologists.
https://en.wikipedia.org/wiki/Hidden_sector
The scary thought is that, were it true that there is voluminous richly-interacting dark matter, we would be the actual dark sector.
I can imagine other scary thoughts, though. Ever read any Warhammer lore?
https://arxiv.org/abs/0903.0660v1
That's more than 3σ.
"Basic" gravitational equations applied to observed behaviour: clumping and rotation of galaxies, lensing (light bending), etc.
The behaviour implies "something" is exerting force in a mass like way - but there's no visible mass.
Physics "allows for" various types of particles with various types of properties - these may or may not all exist, some do.
Neutrino's from the sun barely interact with anything, consistently capturing them is a challenge.
The observational hole left by the apparent behaviour of "unseen matter" attracts a lot of theory.
The opening paragraphs of, say, https://en.wikipedia.org/wiki/Dark_matter cover the ground of speculation.
[1]: https://pirsa.org/26030070
When your equations are missing a number to work, you announce a new particle.
It takes only a small amount of knowledge of physics to understand why and how dark matter might be possible, even likely. So small, in fact, that I can describe it in this comment.
The tl;dr is that all the senses you experience - sight, touch, smell, taste, and hearing - depend on the electromagnetic (EM) interaction. Touch, smell, taste, and hearing all depend on how electrons interact, and sight depends on how photons interact with electrons. But EM is only one of four fundamental interactions that we know of. We humans are essentially blind to all the others, without using devices to detect their presence.
But using devices we've invented, we can detect all sorts of things that we can't detect directly with our senses. X-rays and gamma rays, for example. But those are still just high-energy photons, not a different kind of particle altogether. They just help illustrate how limited our senses are.
A better example is the neutrino. They're pretty close to being "dark matter," because they don't interact via electromagnetism. As a result, they can pass right through your body, because there's nothing much to stop them. You're just as invisible to a neutrino as a neutrino is to you. It's estimated that about 100 trillion neutrinos pass through your body each second.
But neutrinos aren't perfectly "dark" - although they don't interact with electromagnetism, they do interact via the weak nuclear interaction, which is mostly something that happens inside the nuclei of atoms. (They also interact via gravity, but they have very small mass, so that doesn't help us detect them.)
We can detect neutrinos by building huge tanks full of very pure substances like water or argon, and burying them deep underground, to shield them from other interference. We can then look for the tell-tale signs that occur when a neutrino just happens to have a direct hit on an atomic nucleus, something that doesn't happen very often because nuclei are very small. That's why we need large tanks - to increase the odds of a hit.
The IceCube neutrino detector in Antarctica (https://icecube.wisc.edu/science/icecube/) extends to 2.5 km underground, and Super-Kamiokande in Japan (https://www-sk.icrr.u-tokyo.ac.jp/en/sk/) is buried 1 km below a mountain. They're able to detect neutrinos with high confidence, because aside from the tell-tale sing we can often even relate the neutrinos they detect to astronomical sources such as supernovae and supermassive black holes.
Neutrinos show that it's possible to have matter that doesn't interact via electromagnetism, which is all but invisible to us. And not just invisible - it can pass right through us. In the case of neutrinos, we're just "lucky" that they participate in the weak nuclear interaction, so we can detect them if we try hard enough. But what if a particle didn't do that? Then you'd have real dark matter - particles that we can't detect at all, except via the energy they carry, which participates in the gravitational interaction. But it's very difficult to detect tiny particles using gravity - which is why the first place we think we've detected dark matter is at large scales, in the motion of galaxies, where the collective mass of dark matter is large enough to be detected.
With all this in mind, a question dark matter skeptics would need to answer is, why wouldn't we expect dark matter to exist? We've identified quite a large zoo of particles, and what distinguishes each of them is that they each participate differently in the different interactions that we know about. Here's a little table to illustrate that:
Particl...
It's an open question, right, whether dark matter has no interaction or just very little interaction with normal matter? If there's none, this experiment will detect nothing but noise.
I'm confused why, if dark matter exists and has mass (since it interacts gravitationally), there's no noticeable missing results from high-energy events that create particles. Shouldn't dark matter particles be generated by, say, cosmic ray collisions? Or black hole decay?
Correct. What this experiment (LUX-ZEPLIN) is looking for is the effects of xenon nuclei being "bumped" - recoiling - due to something undetectable. It doesn't matter what interaction mediates the recoil - it could even be a so-far-undiscovered interaction. They're just looking for evidence of the recoil happening. But if the only interaction is gravity, they won't detect anything, since gravity is too weak for us to detect the effects of at that scale.
> I'm confused why, if dark matter exists and has mass (since it interacts gravitationally), there's no noticeable missing results from high-energy events that create particles.
Particle physicists actively look for this, e.g. in reactions in particle accelerators. But not finding evidence of that only places constraints on how strongly dark matter can couple to ordinary matter, it doesn't rule it out.
> Shouldn't dark matter particles be generated by, say, cosmic ray collisions?
Not necessarily. Just being energetic doesn't guarantee anything. There's a bit of a chicken-and-egg issue here: without knowing more about dark matter, we can't predict what reactions might produce it. That's why experiments like LUX-ZEPLIN make as few assumptions as possible - all it requires is that some mechanism for energy transfer from dark matter to matter exists.
> Or black hole decay?
Black hole decay has never been observed. Since it's purely theoretical, no matter how well-justified it is, it doesn't really help in the search for dark matter. There's no reason that Hawking radiation couldn't include dark matter, in fact if dark matter exists it probably would, but we have no way to detect that.
Even if say black hole collisions (which have been indirectly observed) produced dark matter, we wouldn't really have any way of detecting it at the distances in question.
> My intuition
> I really assume
hmmmm
I wouldn't go into a neurological medical thread, and post "I'd guess it doesn't even exist" as a solution for Alzheimer's. But you just did the same, analogously.
The reason we haven't mapped the seafloor is because why would we? It's like arguing we know nothing about biology because we've only sequenced the genome of a fraction of humans or something. It's not that we can't do it, the reason we haven't done it is because there's no good compelling reason to do it. What do we expect to learn from mapping 100% of the sea floor?
As for the parents question – "How many years until we've discovered "everything"?"
I think we may be fairly close to knowing everything we can know and it's quite reasonable to assume we're now comfortably on the tail end of the S-curve of physics discoveries. I hope I'm wrong of course.
Just given dark matter and energy, things the standard model doesn't answer, and our evolving tools (e.g. Grace telescope, etc.).
Why would we map the seafloor is an insane question that immediately invalidates all other opinions that you may have, unfortunately. The human embodiment of that meme with the pickaxe guy walking away from a diamond strike if only he had swung once more.
It's so hubristic to assume that our generation is the one that will discover the answers to everything.
I think maybe I was assuming the parent was referring specifically to physics discoveries while you were assuming that they were asking more broadly about how many years until we've discovered everything discoverable?
Unless you are actually arguing there's likely lots of physics discoveries to be made because humans have only photographed a fraction of trees on the earth, or mapped a fraction of the seafloor, or sequenced only a fraction of the genomes of known species.
https://users.ece.cmu.edu/~gamvrosi/thelastq.html
tl;dr: likely as long as the lifespan of the universe.
Has there ever been an article about particle physics that didnt end with a statement about the "next and bigger" version of the current detector. The field has an addiction. No matter the size/luminocity, they will only ever crave a bigger hit.
One wonders if we should measure detectors as we do nuclear bombs: by the kiloton mass of thier detection medium. The DUNE detector would be a 70 kiloton-class detector. Super-Kamiokande, 50kt.
Hopefully, other aparatus elsewhere are big enough too in order to spot similar events.