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It is usually said that neutrinos travel at near c, I suppose there is no precise measurement, but is it known what is the approximate value of its KE?

Also, the mass of a neutrino is 5 million times smaller than an electron, it is already difficult to detect one, do you know how physicists can distinguish between its mass-energy and KE?

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    $\begingroup$ You might as well ask the KE of a photon. It depends. $\endgroup$
    – J.G.
    Sep 7, 2022 at 11:37
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    $\begingroup$ neutrinos need special relativity four vectors hyperphysics.phy-astr.gsu.edu/hbase/Relativ/vec4.html . A photon with zero rest mass, can be considered to have all its energy as kinetic, as it means "moving", The neutrino has a small mass, so a tiny part of its energy is tied up as rest mass, depending on what energy it has. $\endgroup$
    – anna v
    Sep 7, 2022 at 18:11

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For detectable neutrinos, the KE is simply the total energy for practical purposes: rest energy is negligible. The IceCube neutrino observatory has detected neutrinos of PeV energies. The observed spectrum is extremely broad, with many detections at GeV energies. Other technologies are sensitive to lower energies. There isn't a "usual" energy.

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  • $\begingroup$ thanks, how then they can establish that the mass of the neutrino is 0.1 eV? $\endgroup$
    – user337596
    Sep 14, 2022 at 11:22
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We do not know the exact mass of any of the three neutrino species. What we do know of their masses comes from the oscillations of one species into another. Neutrinos are emitted and absorbed in in flavor eigenstates which are combinations of the mass eigenstates. The travel as mass eigenstates and so rate at which they change species depends of the masses and the mixing angles.

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  • $\begingroup$ We also have an upper limit from beta decay. $\endgroup$
    – John Doty
    Sep 14, 2022 at 11:47

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