The Wikipedia article is a decent intro to the general challenge: https://en.wikipedia.org/wiki/Neutrino_detector https://en.wikipedia.org/wiki/Neutrino_detecto

The Wikipedia article is a decent intro to the general challenge: https://en.wikipedia.org/wiki/Neutrino_detector https://en.wikipedia.org/wiki/Neutrino_detector The paper this article is referencing includes a citation to a much longer paper about FASER itself that explains more about how it is designed and why: https://arxiv.org/pdf/2207.11427.pdf https://arxiv.org/pdf/2207.11427.pdf The gist of it seems to be this was the first attempt to put a neutrino detector n nthe director line of sight of a particle collider where they're produced. The LHC's other detectors have blind spots where the neutrinos are produced. The general challenge with neutrinos is they don't interact via the electromagnetic force. This is what is meant when we say they just "go through" normal matter as if it wasn't there. Because mostly, it isn't. Matter is overwhelmingly empty space. It's the large interaction radius of the electromagnetic force that causes matter to behave as if it's solid. Electrically-charged particles do not need to be remotely near each other to interact. Neutrino mass is too negligible to detect anything gravitationally, so that leaves us only with the weak force, but that has a tiny interaction radius. They need to make a more or less direct collision, and the things colliding are unimaginably tiny. It's like throwing a bunch of baseballs into interstellar space and seeing if they ever hit anything. But also, the more energy a neutrino has, the more likely it is to interact, and also more likely to have the so-called "charged current interaction" in which it transforms into a regular charged lepton that can be detected. It needs a lot of energy to convert into mass to do that because it has so little mass of its own. So I think it's mostly those two things, somewhat higher concentration and greater energy. But probably mostly the energy. There are already billions of neutrinos passing through every cubic centimeter of the earth every second. The sun produces way more of them than we can ever produce ourselves. I'm not sure this is really the first detection like the article claims, too. The FASER paper says they detected neutrinos from LHC run 2 in 2018.