Experimental Evidence for Non-Conservation of Parity and Charge Conjugation in Beta Decay

Authors(s):C. S. Wu Publication:Proceedings of the Rehovot Conference on Nuclear Structure Publication Date: Publisher: Citation: Link:
Introduction. Dr. Lee has just given us an excellent talk on the theoretical implication of parity non-conservation in β-decay. He also outlined the various experimental evidences which one would expect to observe under various combination of the coupling constants. The maximum number of coupling constants to be determined thus has leaped from a mere five for the old theory to thirty five or thirty eight in all at the present state. Fortunately, possible means and methods for the investigation of these coupling constants are also greatly increased and extended. The field of β-decay suddenly finds itself bustling with activity and enjoying its unprecedented prosperity. Almost every few days a new method of investigation is conceived and developed, and new results follow immediately. In the brief period of the past few months, many beautiful results have already been reported and the general picture is gradually taking shape. We don’t deny the existence of much apparently conflicting evidence. But Rome wasn’t built in a day, and this is just the very beginning.
2. Why our Previous Knowledge of β-decay Failed to Provide the Evidence for Parity Non-Conservation. Prior to the time when the question of parity conservation in weak interactions was raised, we were contentedly investigating phenomena such as allowed spectra, unique forbidden spectra, forbidden spectra with allowed shapes, β-neutrino collation and β-γ correlation. However, Lee and Yang pointed out that none of these numerous experiments could provide an answer to the party question. The reason is that these phenomena contain no interference terms between coupling constants for the parity conserving and the parity non=conserving interactions. One must measure a pseudo scalar formed out of the experimentally measured quantities.