Richard P. Feynman

In 1957, the American theoretical physicist developed the V-A theory of the weak interaction, simultanteously with others, calling into question the validity of the Rustad-Ruby experiment. He later won the Nobel Prize for his role in the development of quantum electrodynamics. His popular memoir Surely You're Joking, Mr. Feynman relates the events leading up to the V-A discovery, including his comments on the He-6 recoil experiment.

The 7 Percent Solution

Richard P. Feynman
Surely You’re Joking, Mr. Feynman
Jan 1 1985

pp. 226-234
Feynmann’s aha moment was when he saw the figure in Rustad-Ruby


I went to Professor Bacher and told him about our success, and he said, “Yes, you come out and say that the neutron-proton coupling is V instead of T. Everybody used to think it was T. Where is the fundamental experiment that says it’s T? Why don’t you look at the early experiments and find out what was wrong with them?”

And when I became interested in beta decay, directly, I read all these reports but the “beta-decay experts,” which said it’s T. I never looked at the original data; I only read those reports, like a dope. Had I been a good physicist , when I thought of the original idea back at the Rochester Conference I would have immediately looked up “how strong do we know it’s T?”—that would have been the sensible thing to do. I would have recognized right away that I had already noticed it wasn’t satisfactorily proved.

Theory of the Fermi Interaction

R. P. Feynman and M. Gell-Mann
Physical Review
Sep 16 1957

Feynman calls for He6 experiment to be reviewed
Classic VA paper beat Marshak-Sudarshan to publication.


At the present time several beta-decay experiments seem to be in disagreement with one another. Limiting ourselves to those that are well established, we find that the most serious disagreement with our theory is the recoil experiment in He-6 of Rustad and Ruby x indicating that the T interaction is more likely than the A. Further check on this is obviously very desirable. Any experiment indicating that the electron is not 100% left polarized as x for any transition allowed or forbidden, would mean that (8) and (9) are incorrect.

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