Hardy J C, Towner I S
Cyclotron Institute, Texas A & M University, College Station, Texas 77843, USA.
Phys Rev Lett. 2002 Jun 24;88(25 Pt 1):252501. doi: 10.1103/PhysRevLett.88.252501. Epub 2002 Jun 6.
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.
通过超允许核β衰变得到的V(ud)的最精确值导致卡比博-小林-益川（Cabibbo-Kobayashi-Maskawa）幺正性违反了2.2个标准差。在两大洲正在进行实验，通过对A≥62的奇奇N = Z核的衰变研究来检验和改进这一结果。我们在一系列说明性的壳模型计算中表明，预计在这些核中的每一个中，许多弱伽莫夫-特勒（Gamow-Teller）分支将与超允许分支竞争。尽管总的伽莫夫-特勒强度很大，但许多单个分支将弱到无法观测。因此，如果要以0.1%的精度获得超允许分支的可靠ft值，就必须开发新技术。
