How can there be antineutrinos?

[KeplerJunior]

I was wondering how it is possible for there to be anti-neutrinos when antimatter is is identical to matter apart from having the opposite charge. However neutrinos have 0 charge so how can they have anti-neutrinos.

 

[mathman]

The difference between matter and antimatter is not just opposite charge. Antineutrons exist, being made of antiquarks.

The question about antineutrinos is whether or not they are the same as neutrinos.

 

[bcrowell]

Antineutrinos have fermion number -1. So a neutrino can annihilate with an antineutro, but not with another neutrino.

Also, I could be wrong about this, but I believe neutrinos have nonvanishing magnetic dipole moments, and the directions of these relative to the spin would be opposite in the two cases.

 

[Naty1]

It seems there is pretty good evidence for anti neutrinos...it seems thay have been detected. So far observations indicate they have spin opposite that of the left hand neutrino spin.

 

[jtbell]

The way you tell neutrinos and antineutrinos apart in accelerator experiments is to smack them into something and see what comes out. If it includes one net negative lepton (e-, mu- or tau-), you had a neutrino. If it includes one net positive lepton (e+, mu+ or tau+), you had an antineutrino. These interactions proceed via a virtual W boson ("weak charged current interaction").

If you get no leptons coming out, or an even number of them, but there's a lot of "missing" energy and momentum, then you probably had a neutrino or antineutrino coming out, and you can't really tell the difference. These interactions proceed via a virtual Z boson ("weak neutral current").