Superallowed beta decay of nuclei with a >or= 62: the limiting effect of weak Gamow-Teller branches

The most precise value of V(ud), which is obtained from superallowed nuclear beta decay, leads to a violation of Cabibbo-Kobayashi-Maskawa unitarity by 2.2sigma. Experiments are underway on two continents to test and improve this result through decay studies of odd-odd N = Z nuclei with A>or=62....

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Bibliographic Details
Published in:Physical review letters 2002-06, Vol.88 (25 Pt 1), p.252501-252501, Article 252501
Main Authors: Hardy, J C, Towner, I S
Format: Article
Language:English
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Summary:The most precise value of V(ud), which is obtained from superallowed nuclear beta decay, leads to a violation of Cabibbo-Kobayashi-Maskawa unitarity by 2.2sigma. Experiments are underway on two continents to test and improve this result through decay studies of odd-odd N = Z nuclei with A>or=62. We show, in a series of illustrative shell-model calculations, that numerous weak Gamow-Teller branches are expected to compete with the superallowed branch in each of these nuclei. Though the total Gamow-Teller strength is significant, many of the individual branches will be unobservably weak. Thus, new techniques must be developed if reliable ft values are to be obtained with 0.1% precision for the superallowed branches.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.88.252501