Chien-Shiung Wu

The woman widely viewed as the greatest experimental physicist of her time was not yet a tenured professor at Columbia University when she supervised Stanley Ruby's research for his Columbia doctoral degree, published in 1953 with Brice Rustad as collaborator. Wu achieved her breakthrough in 1956 when her experiment confirmed the violation of the law of parity conservation in beta decay interactions. That set off a chain of events that resulted a year later in Wu's unpublished critical reappraisal of the Rustad-Ruby experiment, a hiccup on her away to storied scientific and professional success.  

Beta Decay

C.S. Wu and S.A. Moszkowski
Sep 1 1966

Wu's more distant review of the He6 events


Evidence for V—A Interaction. Suddenly many doors swung open to lead to the determination of the β interactions.

The early experimental results indicated that a is close to +1/3, favoring a tensor interaction. However, more recent experiments (He-58; Al-59), whose arrangements are shown in

Prove. Inclusively that coefficient a in Gamow-Teller is negative, being in fact close to the expected value of -1/3 for the axial-vector form. This result has been confirmed by the Oak Ridge group (Jo-63) with a more refined setup

A Critical Examination of the He-6 Recoil Experiment of Rustad and Ruby

C. S. Wu and A. Schwarzschild
Columbia University Dept. of Physics internal report
Apr 21 1958

Wu repudiates Rustad-Ruby experiment in unpublished CU-173 Columbia University report. Franklin says letter from Wu to Cavanaugh suggests reexamination was done in November.


The latest results of A-35 strongly indicate a vector-interaction in Fermi transition. The evidence of the recoil experiment of He-6 by Rustad and Ruby has been considered rather conclusively for tensor interaction. So here we are in a predicament!  
It is therefore highly desirable to look carefully into the He-6 experiment and decide whether any systematic errors due to oversight could have affected their interpretation

The following is a report of such an investigation, and the conclusion is that unfortunately some corrections which the authors neglected in their calculations turned out to be quite substantial and rendered the conclusion which they originally made definitely questionable.

The purpose of the re-examination is to point out the detrimental effects on the correlation results due to the presence of even a small quantity of He-6 gas in the diaphragm holes. Furthermore, by using an optical analog it has been possible to infer directly the pressure gradient of He-6 along the chimney hole and therefore substantiate our supposition. This is, unfortunately, what happened.

Acknowledgments. We wish to thank Dr. Richard Garwin and Dr. Luke Yuan for many valuable discussions concerning the measurement of the gas pressure gradient. We particularly want to thank Mr. K. Lattemann for his patient help in carrying out the investigation of the angular variation effect. To Mr. B. Rustad and Mr. S. Ruby we express our thanks for their cooperation. 

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

C. S. Wu
Proceedings of the Rehovot Conference on Nuclear Structure
Sep 10 1957

Wu obliquely refers to classic experiments but focuses on post-parity work


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 Beta-Spectrum of S-35

R. D. Albert and C. S. Wu
Physical Review
Aug 19 1948

Representative of many beta spectrum studies Wu did with collaborators throughout this period


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