Deep under Antarctic ice, a long-predicted cosmic whisper breaks through | Hacker News Reader

Deep under Antarctic ice, a long-predicted cosmic whisper breaks through

phys.org

134 pointsrbanffy45 comments

I was involved in this analysis if anybody has questions (though the student and postdoc did most of the real work)

original article: https://arxiv.org/abs/2510.21104 or https://journals.aps.org/prl/abstract/10.1103/xwqy-yzrk

All these high energy particles travel at tremendous speeds, and for them it looks like you traveled half the Universe in a fraction of a second. And then you've hit an Antarctic ice. I think I'd be extremely excited at this, because I'm sure any particle dreams about becoming alive, and falling on Earth give pretty solid chances to integrate into a living organism. And even maybe to fly to the Moon then, to build a base there! I always wonder what are they... I can't stand these romantic stories without knowing more about the heroes.

Is there any hope to have know more about them? To point at some and say "they are neutrinos" is a big promising step, but what about others? Was it a proton, or neutron, or electron or what? Where did this particle come from, and who was so pissed off to kick it that hard. I mean, I read wikipedia a lot, I have an idea what kind of processes can create these particles, but if we could find an extremely red shifted galaxy on a photo from James Webb and say that THAT proton came from there, it would be very nice.

To be clear, the detection here is of a mundane cosmic ray that started interacting in the upper atmosphere, but came at such an angle (and the Antarctic plateau is high enough) that the cascade it started continued into the ice.

But yes, one of the main reasons we are looking for ultra-energetic neutrinos is to try to understand the sources of high energy particles in general, as the highest energy charged particles are harder to point due to bending in magnetic fields. Measuring UHE protons from high red shifts is not possible due to the GZK mechanism, but that same mechanism will produce neutrinos that we are hoping to detect!

Particles don't like being anthropomorphized.

Summary for those who won't fight through four blocking pop-ups to read the article:

When a high-energy particle (cosmic ray, say) hits ice, it creates an interaction cascade. (Think of what the Fly's Eye experiment sees, but in ice.) That interaction cascade creates (among other things) a radio signal. This detector is a radio detector under Antarctic ice, looking for exactly that.

The point is that, if a high-energy neutrino were to hit the ice, it could create the same kind of cascade, but it would make it much further into the ice. By having multiple detectors, they can pin down the location, and so they can try to tell the difference between "regular" cosmic rays and high-energy neutrinos.

The detector seems to be functioning as designed. They have seven candidate neutrino interactions.

I just turned off my ad blocker to see how bad it is. Because with it turned on I didn't see any popups.

They have Google ads on their site promoting a paid ad free version of their site? WTF? Why would you pay google to put ads for on your site for your own service?

Let me clarify, as someone involved in writing this paper.

This radio emisison (Askaryan emission) is the mechanism by which we hope to detect neutrinos with detectors like ARA (and also PUEO, RNO-G, etc. which I also work on :) ), but these events are actually candidate impacting cosmic rays. UHE cosmic rays (protons, and heavier nuclei) are charged particles that will start cascading in the atmosphere, but in certain near- vertical geometries, the shower is not "expended" before reaching the ice (which lies at an altitude of ~3km), so the dense shower core enters the ice, producing radio emission from the same mechanism through which we hope to detect neutrinos. While the Askaryan mechanism was detected in ice in beam line experiments and also in the atmosphere (where it is subdominant to radio emission from charged particles bending in the Earth's magnetic field), this is the first detection of the Askaryan effect in natural ice, proving that the emission matches our models. The cosmic rays themselves are not super interesting in the sense that there are other detectors that are much better at detecting cosmic rays (e.g .TA or Pierre Auger).

Follow up question: So if it's a cosmic ray, it has to be near vertical, or it would interact with the atmosphere and never make it to the ice? So if it's far from vertical, then it was a high-energy neutrino? Do I have that right?

It has to be nearish vertical (how close depends on energy, but it's a pretty wide band around vertical) so that all of its energy is not absorbed in the atmosphere. As you get closer to horizontal trajectories you go through way more atmosphere. Neutrino-induced cascade would typically be initiated within the ice , not at the surface (in principle they could be at the surface but we would reject them since it's much more likely that it's something else in that case).

> With a new data release expected soon, covering all five ARA stations over several years, the ARA team now anticipates up to seven candidate neutrino events.

I love the patience involved in this kind of science.

that's... one way to put it :)

The 5-station analysis covering a number of years is coming out soon (but searching for neutrinos, not impacting air showers, which is what this PRL is about) .

Is it just ice? I thought most neutrino detectors were large underground pools of water. I mean ... tomāto/tomăto, yes, but is solid water better than liquid water?

The size of the detector can be very large, stable, and protected with an ice cap. https://icecube.wisc.edu/science/icecube/

There aren't a lot of places with multiple km of water without things like animal life or other confounders.

So, [controlled] liquid water is better but [controlled] solid water is more abundant?

I wouldn't say liquid is "better". The neutrinos don't care from a cross section standpoint.

Uniformity of the light field is going to be different, but that is not my sub-domain.

A liquid you control (and can densely instrument) is going to be a much easier to characterize detector than large volumes of natural material

Wouldn't the higher density of liquid water be an advantage?

It's quite a minor difference

Depends on the energy scale involved!

Higher energy = "easier" to detect (produce more light or radio emission), but the events are rarer so you want to build a bigger detector.

There are also underwater pools of water being used :) (KM3Net,P-ONE, Baikal-GVD, etc.)

For radio detection, solid water is better because it has a much much longer radio attenuation length.

Cough, Cough. (Dusting off my Hacker News Fan Boy Hat.)

I just want to come round again to how amazing it is to have a small slice of the internet where “amazeballs scientific discovery happens” and we get, of course, someone on the site who has been part of it.

(Hat goes back in box)

I often feel like HN is the last true remnant of the old internet. Very grateful that it still exists in its current form.

Ah, I thought it would be a dark matter/energy signal...

Why so many authors?

Everyone in the collaboration is an author. This is typical for particle physics collaborations. Not everyone contributed directly to this analysis of course, though everyone's feedback was solicited. Some people contributed to construction, instrument design, deployment, calibration, operations, monitoring, maintenance, common data processing tools, etc. the acknowledgements list the people who did most of the work but even they were advised by a larger group of people (I was one of them :) ).

Note that the author order is alphabetical but one of the primary authors happens to be first alphabetically.

Pluribus, be careful

like the start of a sci-fi movie

Just read the title and thought "Not now Cthulu, we've got enough going on"

Whereas i was thinking "it's about time a hero arrived!" ;)

i don't presume to know whether Cthulhu is the hero we need or the hero we deserve.

Definitely the one we deserve...

Next time I go to the site to dig out a station, maybe I'll leave a Ctulhu to surprise the next person :)

we didn't start the fire

it was always burning since the world was turning

But we definitely tried our best to extinguish it with gasoline.

To be fair, that’s the recommended way to put out an alkali metal fire. At least according to my grandfather who helped write safety regulations for nuclear subs whose reactors were cooled by liquid sodium.

Not really something I’d want to try out in practice, seems like a fire in a nuclear reactor under the ocean, where the source of the fire explodes on contact with water, is a less-than-ideal situation.

Not a bad metaphor for the times, though.

That is indeed the second best way to extinguish them. The best when seeing alkali metal burning is a good pair of running shoes.

Running shoes won't help you much in a nuclear submarine.

it's important to remember - it has always felt like that

Cthulu is supposed to rise and induce madness in the population, driving them towards death and destruction right? Seems like he'd be bored these days

Earth, 2026. Silently shifting through the mysterious dimensional plans, Cthulhu just jumped in. Thinking it could unleash new level of despair and frights on the mere mortal souls inhabiting this world, it was anticipating it's own jubilation. Throwing a glance omnivision on it however, all sense of joy suddenly vanished from its monstrous mind and to its own surprise, despair was invading it as it was contemplating situations far more awful than what it had ever devised. All self inflicted by small almost-thoughtless meat bags. Shifting back, it tried to convince itself this never happened and in the same time, promise itself to never land again on this desolated place.

At this point I am more than willing to hear his political platform.

https://cthulhuforamerica.com/

America First, then the rest of the world. Love it. Thanks for this. Already spreading it.

I thought of The Thing...

Does the study mention if all their dogs are accounted for and acting normally?

If you think someone has a heart attack, do not do CPR.

Probably more likely to run into a Shoggoth than Cthulhu in the Antarctic, or maybe an Elder Thing if any are still around. Rl'yeh is a bit further north.

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