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Question: how do we know where (what direction, orientation, velocity) neutrinos come from? (lemmy.world)

submitted 3 months ago by Donjuanme@lemmy.world to c/science@lemmy.world

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I've seen a few articles about neutrinos recently, high energy ones, super fast ones, ones from open space, others from "sources", and my understanding of the particle is that it's very hard to detect, passes through light-years of lead without interaction, etc. don't headings and speed require multiple readings to make? How do we know the velocity of a neutrino when we can only detect them at single points?

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[–] bjoern_tantau@swg-empire.de 2 points 3 months ago

If I understand it correctly we detect them when they let an atomic nucleus decay in some transparent material like water or ice. The decay produces an electron and a positron which annihilate to a photon. Because momentum is conserved that photon continues traveling in the same direction as the neutrino. And with the same speed which is close to C and usually faster than the speed of light in water, which releases Cherenkov radiation, basically a sonic boom but with light.

Somebody please correct me if I got something wrong.