Chien-Shiung Wu and collaborators tested parity conservation by measuring the beta decay of oriented cobalt-60 nuclei at very low temperature. Their apparatus placed a beta counter inside a demagnetization cryostat and used the accompanying gamma ray anisotropy to monitor nuclear orientation. The emitted electrons favored one direction relative to the nuclear spin. Because parity reverses momentum while leaving angular momentum unchanged, that directional asymmetry distinguishes a process from its mirror image and demonstrated parity violation in the weak interaction.[ref]
Experimental Test of Parity Conservation in Beta Decay by Chien-Shiung Wu and others. Opening argument, Fig. 1 cryostat and observed electron asymmetry
A physicist.[ref]
The Fall of Parity Photo Gallery with Short Biographies by National Institute of Standards and Technology. Independent professional profile
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Chien-Shiung Wu (1912-1997) was a prominent Chinese-American experimental physicist who made significant contributions to the field of nuclear physics. She is best known for her work on the properties of beta decay and for conducting the Wu experiment in 1956, which provided crucial evidence for the theory of weak interaction and demonstrated that parity is not conserved in weak nuclear processes.
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