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.

Or this[2] 2007 Science paper on ultra high energy cosmic ray source candidates ("anisotropy") that we had to retract because significance started dropping almost the day the paper was approved.

It was a fascinating experience as a junior member to follow the collaboration internal conversation and investigation on this, because a lot of extremely principled scientists were clearly deeply worried about losing their hard earned reputation. In the end, I am convinced that we were simply unlucky.

[2] https://arxiv.org/pdf/0712.2843

> 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.

Are there any other candidate particles besides WIMPs that the observation could be from, assuming it’s a real signal?

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.

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.

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.

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.

Whether or not they've "seen" 3x more events is a little bit of a tricky question, because while they may have captured 3x the data exposure (see sibling comments) experiments often operate blinded to the data. They can develop their analysis scripts, play out various different scenarios via Monte Carlo simulation, and get their whole pipeline working without the bias of actually seeing how each change in algorithm alters the outcome for the real data.

Then, at some point, they freeze their pipeline, "open the box", run the analysis on the real data, and report what they find. But they can only "open the box" once per exposure, after that you can worry that human bias can creep in.

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.

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.

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!

Astronomy/Physics is overflowing with unexplained physics phenomena these days.

Especially after JWT started looking deeper into the early universe.

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.

To start with, they do a lot of work to eliminate radioactive backgrounds in the materials they're using, and they put the detector deep underground to shield from cosmic rays.

Additionally, when a particle interacts with the nucleus, the ratio of how much energy ends up as scintillation light versus ionization is different than when a particle interacts with an electron, which is most of the background processes.

Then, whatever is left, they try to model using known processes. After all that, there's one event that they can't account for. And that's what the news is about.

I've heard this referred to as a "dark sector", or "hidden sector":

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.

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.

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.

You might like this old paper then:

https://arxiv.org/abs/0903.0660v1

Probably never. We've only mapped like 29% of the seafloor, actually explored like %5 of it, and we've barely pierced the earth's crust.

You can know all the whats and hows and still have no clue about why

May I strongly suggest you to read Asimov’s short story The Last Question for an answer.

https://users.ece.cmu.edu/~gamvrosi/thelastq.html

tl;dr: likely as long as the lifespan of the universe.

> LZ physicists estimate there’s about a one in 200 chance the event is a statistical fluke

That's more than 3σ.

Depending on the size of the black holes these detectors can see them.

The total cost of this experiment may be a lot less than you expect. I'd encourage you to make a guess as to what you think it could cost the US taxpayer and then check what the Department of Energy contributed [1].

The LZ collaboration is going to run their machine until at least 2030. They have almost no hope of making a meaningfully larger detector, no will you hear them suggest one. Their detector is already designed at such a scale that it contains a substantial fraction of all the needed xenon isotope available on Earth.

[1] https://news.wisc.edu/dark-matter-detection-receives-10-ton-...

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.

> No idea what equations are used for getting to the result

"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 a shortfall of visible mass.

The observational hole left by the apparent behaviour of "unseen matter" attracts a lot of theory.

* Physics "allows for" various types of particles with various types of properties - these may or may not all exist, some do. eg: Neutrino's from the sun barely interact with anything, consistently capturing them is a challenge. Maybe Dark Matter is a new hard to observe gravity particle.

* Physics has equations formed by "human scale" observation and sometimes tweaked for scales beyond direct human experience. eg: relativistic tweaks related to speeds approaching that of light. Maybe Dark Matter is a warping of observation at galaxy scale.

The opening paragraphs of, say, https://en.wikipedia.org/wiki/Dark_matter cover the ground of speculation.

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.

[1]: https://pirsa.org/26030070

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 have zero knowledge of physics

> My intuition

> I really assume

hmmmm

400 years ago you'd be saying the same thing about heliocentrism.

“constant missing in our math” is roughly how inventing new particles in physics works.

When your equations are missing a number to work, you announce a new particle.

> I just can't believe something like dark matter exists.

That's a lot like a blind person saying they can't believe light 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 summary of the fundamental particles and their participation in the fundamental interactions - which are gravity, electromagnetism (EM), weak nuclear, and strong nuclear (the latter two are different types of interactions that happen to have very generic names):

Electron: gravity, EM, weak

Neutrino: gravity, weak

Photon: gravity, EM

Quark: gravity, EM, weak, strong

Gluon: gravity, strong

Dark matter: gravity, ?

There's no physical reason we wouldn't expect a particle like dark matter to exist. It doesn't even have to have no interaction other than gravity - 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.

If you accept the existence of X-rays and neutrinos, then it's not very consistent to draw the line at dark matter, once you have some understanding of the physics involved.