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Comment by AnimalMuppet | Hacker News Reader

Then I don't understand something. (Or several somethings...)

I thought you said that going to antimatter meant that you reversed chirality, and that right-handed chirality meant that a particle did not take part in the weak interaction. I interpreted that to mean that it didn't take part at all, not with any probability. But the CP violation article seems to be saying that CP violation is a matter of differences in probabilities.

By the way, that article talks about anti-neutrinos, which from your initial post, I thought you were saying were impossible to detect if they existed?

I'm confused... can you make any of this clearer? I'm mis-understanding something - can you tell what?

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Given a fermion species, let's say an electron, you can have:

- left-handed electron

- right-handed electron

- left-handed anti-electron

- right-handed anti-electron

Going from particle to anti-particle, you swap charge and chirality (that's the CP transformation). So for instance a left-handed electron with negative electric charge becomes a right-handed anti-electron with positive electric charge.

For neutrinos, given that left-handed neutrinos have weak interactions, then so do right-handed anti-neutrinos.

It's no harder to detect anti-neutrinos than neutrinos. It's right-handed neutrinos and left-handed anti-neutrinos you'd have a problem with.

The CP violation article talks about probabilities because CP violation is not nearly as neat as P violation alone. Instead of the clear-cut "left-handed neutrinos (and therefore right-handed anti-neutrinos) only" of P, you get small differences.

Thanks! I think that was what I needed.

One last question: I was under the impression that the difference between a neutrino and an antineutrino was only chirality. What other property is there to distinguish a neutrino from an anti-neutrino?

Weak isospin. Look at the table in

https://en.wikipedia.org/wiki/Weak_isospin#Relation_with_chi...

(including the text in the last two rows).

Thank you for your knowledge, patience, and persistence in these answers.

That was an amazing discussion. Thank you both.

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