2020 Impact factor 3.043
Hadrons and Nuclei
Eur. Phys. J. A 15, 229-232 (2002)
DOI: 10.1140/epja/i2001-10259-y

Tests of the standard model from superallowed Fermi $\mth{\beta}$-decay studies: The $\chem{^{74}Rb}$ $\mth{\beta}$-decay

E.F. Zganjar1, A. Piechaczek1, G.C. Ball2, P. Bricault2, J.M. D'Auria3, J.C. Hardy4, D.F. Hodgson5, V. Iacob4, P. Klages6, W.D. Kulp7, J.R. Leslie8, M. Lipoglavsek9, J.A. Macdonald2, H.-B. Mak8, D.M. Moltz10, G. Savard11, J. von Schwarzenberg7, C.E. Svensson12, I.S. Towner8 and J.L. Wood7

1  Louisiana State University, Baton Rouge, LA 70803-4001, USA
2  TRIUMF, Vancouver, B.C., V6T 2A3 Canada
3  Simon Fraser University, Burnaby, B.C., V5A 1S6 Canada
4  Texas A&M University, College Station, TX 77843, USA
5  University of Surrey, Guildford, Surrey, GU2 7XH UK
6  McMaster University, Hamilton, Ontario L8S 4L8 Canada
7  Georgia Institute of Technology, Atlanta, GA 30332, USA
8  Queens University, Kingston, Ontario, K7L 3N6 Canada
9  Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA and J. Stefan Institute, 1000 Ljubljana, Slovenia
10  Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
11  Argonne National Laboratory, Argonne, IL 60439, USA
12  University of Guelph, Guelph, Ontario, N1G 2W1 Canada

zganjar@rouge.phys.lsu.edu

(Received: 21 March 2002 / Published online: 31 October 2002)

Abstract
Precise measurements of the intensities of superallowed Fermi $0^{+}\rightarrow{0}^{+}\beta$-decays have provided a powerful test of the CVC hypothesis at the level of $3\times10^{-4}$ and also led to a result in disagreement with unitarity for the CKM matrix at the 98% confidence level. It is essential to address possible trivial explanations for the apparent non-unitarity such as uncertainties in the isospin symmetry-breaking corrections. We have carefully studied the 74Rb $\rightarrow^{74}$Kr $\beta$-decay in order to measure the non-analog $\beta$-decay branching to the 0+ state at 508 keV in 74Kr. We have determined that this branching is $<3\times10^{-4}$, far smaller than any published theoretical estimate. We also show that high-precision, complete spectroscopy, measuring the major $\beta$-branches to excited 0+ and 1+ states, must be performed if one is to obtain a meaningful branching ratio to the excited 0+ state and concomitantly deal, in a substantial way, with the possibility of $\beta$ feeding to an array of 1+ states.

PACS
21.10.-k - Properties of nuclei; nuclear energy levels.
23.40.-s - Beta decay; double beta decay; electron and muon capture.
27.50.+e - $59 \leq A \leq 89$ .

© Società Italiana di Fisica, Springer-Verlag 2002