# Incorrect explanation of parity violation?

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## Main Question or Discussion Point

This APS page http://focus.aps.org/story/v22/st19 describes the classic experiment by Wu et al. in the 50's that demonstrated parity violation. It contains the following explanation: "[1] The magnetism of the nuclei can be thought of as resulting from their spin. With the nuclei aligned with their north poles pointing up, the mirror image would reverse their spin and cause the north poles to point down. But upward-emitted electrons will still move upward in the mirror. So if the decay respected mirror symmetry, electrons should be equally likely to be emitted upwards as downwards."

Isn't this exactly backwards? The magnetic field and the angular momentum are both pseudovectors, which you can see because $L=r \times p$ is invariant under parity (both r and p flip). The velocity vector of the emitted betas is a real vector, not a pseudovector. So under parity, the spin *doesn't* reverse, but the direction of emission *does*.

Or am I just on drugs?

[EDIT] OK, I think I have it. I was assuming that when they said "mirror," they meant total parity inversion, not just inversion in a plane. Inversion in a vertical plane would reverse a vertical L vector but not a vertical v vector.

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