Parity violation in weak decays

[JoePhysicsNut]

I am confused about when and to what extent parity is violated in weak decays.

On the one hand, there's Wu's famous experiment where electrons are emitted preferentially in one direction. This parity violation can be said to be maximal, since all electrons are emitted in one direction.

However, at the same time when determining the angular momentum and spin state of the electron-neutrino system in nuclear β-decay, I do use parity conservation as parity is mostly conserved.

Could anyone explain why parity is violated maximally in the case above and minimally in the other case? Also, to what extent (~0.1%, ~1%, etc of cases) is parity violated in nuclear β-decay?

 

[muppet]

Can you give us an example of someone using parity as a good symmetry when discussing beta decay?

 

[JoePhysicsNut]

Can you give us an example of someone using parity as a good symmetry when discussing beta decay?

As an example, consider the
La_{57} (J^P=2^-) → Ce_{58} (J^P=0^+) decay and I'd like to figure out what the angular momentum and spin state of the electron-neutrino system is.

I get the right answer, when I require l=1 as this carries P=-1 making P conserved and S_{enu}=1 to conserve angular momentum overall.

 

[ofirg]

I think a fermion pair as the (e,\nu) pair has a negative intrisic parity, so with l=1 they should have a total of P=1