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Comment by AnimalMuppet | Hacker News Reader

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.

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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).

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?

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