Parity Violation of Weak Force - Wu et al.

[Master J]

I have read about Wu et al. and their experiments with Co 60 that showed that the weak interaction violates parity. I don't quite get it tho.
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So they aligned Co atoms in a magnetic field. Some of the nuclei decay and emit neutrinos and electrons. It was observed that an equal number of the electrons were NOT emitted parallel and anti parallel to the magnetic field.

How does this show parity violation? I don't quite get how the electron distribution in a magnetic field shows this?

Can anyone elaborate?

 

[The_Duck]

Parity symmetry is the statement that if you look at the universe through a mirror, what you see should obey the laws of physics.

So say you have a mirror. Make a circular loop of wire and hold it in front of a mirror in a plane parallel to the mirror. Run some current through the wire to generate a magnetic field. At the center of the loop, that magnetic field is perpendicular to the plane of the mirror. Say it points away from you and toward the mirror. Place some Co atoms at this location and line their spins up with the magnetic field. When they decay their electrons will prefer to go in one direction, say along the magnetic field direction, that is, away from you and toward the mirror.

Now what do we see in the mirror? We see an image of our wire loop, with current flowing in it. The current you see in the mirror flows in the same direction, so it should generate a magnetic field in the same direction as the real magnetic field, that is, away from you (and towards mirror-you). We know that Co atoms in a magnetic field like to spit electrons out in the same direction the field points. So we expect that the Co atoms we see in the mirror should appear to spit out mirror electrons along the mirror magnetic field, that is, away from you and towards mirror-you. But this can't happen, because the real electrons get spit out away from you, so the mirror electrons, which are really just reflections of the real electrons, must travel away from mirror-you. So what we see in the mirror is /not/ a physical process proceeding according to the laws of physics as we know them. The mirror-world obeys different laws: mirror-electrons tend to get spit out /opposite/ the mirror-field direction. Parity is not a good symmetry.