Where are these neutrino masses coming from?

  • #1
Turnernater
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TL;DR Summary
Is there a typo in the standard model of elementary particles?
Ever since High school I've seen this model of the "particle zoo," including in my recently finished particle physics undergrad course, and I can't seem to find where the mass numbers for the neutrino family is coming from!

Sure the model has a less than sign, but from what I understand all three should easily be around 1ish eV, and much less than MeV like in the picture. I've looked where Wikipedia was getting the data (the particle data group, Fermilab, PBS nova), and those sources also have something in the eV range.

Any idea where the masses for the muon neutrino and tau neutrino are coming from?
 

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  • #2
The flavor states are not mass eigenstates. As such, they do not have definite masses.

That said, there are very stringent limits on all (light) neutrino mass eigenstates to be below 1 eV.
 
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  • #3
As for the values quoted in the image, they are kinematics only limits from direct measurements of various reactions while effectively treating the neutrino involved as if it were a neutrino of a definitive mass. For example, the value quoted for the muon neutrino is based on measuring the muon momentum for the reaction ##\pi^+ \to \mu^+ + \nu_\mu## where the initial pion is at rest.

These limits are generally not competitive with other limits on neutrino masses. The possible exception being the beta decay experiments for ##\nu_e##.
 
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