Standard-Model Tests with Superallowed β-Decay: An Important Application of Very Precise Mass Measurements |
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Authors: | J C Hardy I S Towner |
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Institution: | (1) Cyclotron Institute, Texas A & M University, College Station, TX 77843, USA;(2) Physics Department, Queen's University, Kingston, Ontario, K7L 3N6, Canada |
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Abstract: | Superallowed β-decay provides a sensitive means for probing the limitations of the Electroweak Standard Model. To date, the
strengths (ft-values) of superallowed 0+→0+ β-decay transitions have been determined with high precision from nine different short-lived nuclei, ranging from 10C to 54Co. Each result leads to an independent measure for the vector coupling constant G
V and collectively the nine values can be used to test the conservation of the weak vector current (CVC). Within current uncertainties,
the results support CVC to better than a few parts in 10,000 - a clear success for the Standard Model! However, when the average
value of G
V, as determined in this way, is combined with data from decays of the muon and kaon to test another prediction of the Standard
Model, the result is much more provocative. A test of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix fails by more
than two standard deviations. This result can be made more definitive by experiments that require extremely precise mass measurements,
in some cases on very short-lived (≤100 ms) nuclei. This talk presents the current status and future prospects for these Standard-Model
tests, emphasizing the role of precise mass, or mass-difference measurements. There remains a real challenge to mass-measurement
technique with the opportunity for significant new results.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | atomic mass CKM unitarity CVC hypothesis standard model superallowed beta-decay |
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