Deep under Antarctic ice, a long-predicted cosmic whisper breaks through
63 points - last Sunday at 9:51 PM
SourceI was involved in this analysis if anybody has questions (though the student and postdoc did most of the real work)
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!
> 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) .
psychoslave
today at 4:41 PM
Ah, I thought it would be a dark matter/energy signal...
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
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.)
AnimalMuppet
today at 2:21 PM
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.
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).
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?
like the start of a sci-fi movie
Just read the title and thought "Not now Cthulu, we've got enough going on"
gibsonsmog
today at 4:08 PM
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
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 :)
NooneAtAll3
today at 3:56 PM
we didn't start the fire
it was always burning since the world was turning
ReptileMan
today at 4:10 PM
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.
ReptileMan
today at 4:33 PM
That is indeed the second best way to extinguish them. The best when seeing alkali metal burning is a good pair of running shoes.
ReptileMan
today at 4:09 PM
At this point I am more than willing to hear his political platform.