Wu experiment

A 1956 beta-decay experiment showed that weak nuclear interactions violate parity symmetry by measuring electrons emitted from polarized cobalt-60 nuclei.

Parity symmetry: Parity symmetry is invariance under spatial inversion, which reverses all spatial coordinates. The experiment tested whether beta decay remained unchanged when spatial directions were inverted.
T. D. Lee: T. D. Lee was a Chinese-American theoretical physicist who shared the 1957 Nobel Prize in Physics. Lee helped identify weak interactions as a setting where parity conservation had not been experimentally established.
Chien-Shiung Wu: Chien-Shiung Wu was a Chinese-American experimental physicist known for precision measurements in nuclear physics. Wu designed and led the experiment that established parity violation in beta decay.
Wu–Yang experiment: The Wu–Yang experiment is a 1957 electron-scattering test of parity nonconservation in electron-proton interactions. It tested the same symmetry principle through a different process than cobalt-60 decay.
Weak interaction: The weak interaction is a fundamental force responsible for processes such as beta decay and neutrino interactions. The observed asymmetry showed that this force does not conserve parity.
Chen-Ning Yang: Chen-Ning Yang was a Chinese-American theoretical physicist who shared the 1957 Nobel Prize in Physics. Yang coauthored the 1956 analysis proposing tests of parity conservation in weak interactions.
Ambler, Hayward, Hoppes, and Hudson: Ernest Ambler, Raymond W. Hayward, Don Hoppes, and Ralph Hudson were physicists who collaborated with Wu on the cobalt-60 experiment. These National Bureau of Standards collaborators helped carry out the measurements.
V–A theory: V–A theory describes weak interactions using vector-minus-axial-vector currents and maximal parity violation. The measured asymmetry supported a theory in which weak interactions distinguish left from right.
Cobalt-60: Cobalt-60 is a radioactive isotope that beta-decays to nickel-60 with a half-life of about 5.27 years. Its beta decay supplied the electrons whose directions were measured.
Question of parity conservation in weak interactions: The question of parity conservation in weak interactions concerns whether those processes behave identically under spatial inversion. Lee and Yang’s review exposed the lack of decisive experimental tests that preceded Wu’s work.

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