Induced scalar interaction in the analysis of superallowed fermi ? transitions

Abstract

Nuclear Structure superallowed Fermi/3 transitions; derivation of the coupling constant for the induced scalar interaction fs from experimental data.Very recent works reported a significant improvement in the consistency of Yt values for superallowed Fermi/3-decays. This fact led us to investigate some aspects which are not usually tackled in a study of this kind of transition. In a recent paper we suggested that an upper limit for the coupling constant fs for the induced scalar interaction can be derived analyzing superallowed Fermi /3-transitions. In the present work we revise and improve the method for the determination of fs. The result obtained, fs/fv = (-0.4 __ 1.4)x 10-3, agrees with the prediction of the CVC theory.

Current state of the investigation of superallowed Fermi? decays

“…No evidence for any lingering Z dependence in the experimental data was found in [5,6]. It was thus reasonable [2][3][4][5][6] to evaluate a weighted average of ~t values and subsequently derive a reliable value for the codpling constant G v. We should point out that the test of Z independence was not applied in the work of Wilkinson et al [17] or of Towner and Hardy [22].…”

“…Under such an assumption, namely setting fs to be zero, if 6r is evaluated correctly, we should expect ~t constant from nucleus to nucleus. In our previous investigations [5,6] we tested the constancy of the ~t values over the known /3 decays performing a leastsquares analysis. Searching for a possible small dependence of ~t on the charge of the daughter nucleus, we fitted the Yt values to the formula…”

“…Since the three independent comprehensive papers [24] on 0+-0 + /3 transitions were published in late 1975, new experimental improvements have enabled the experimental errors of the relevant measurable magnitudes to be significantly reduced. In other words, the half-lives t o and the maximum energies of the positron spectra, Wo, can now be measured with increased precision, making it possible to calculate more precisely the quantities involved in the evaluation of thef' t values, namely, Finally, substituting the expression (6) in (3), we obtain K f' t-,2 v 0 2 2' (8) Gv ( …”

“…It has been shown [5,6] that keeping only the large components and assuming, as usual a uniform charge distribution, the Fermi FFC can be reduced to…”

“…In relation to 0+-0 § Fermi decays, the CVC theory predicts that [1][2][3][4][5][6]: (a) the vector coupling constant of the weak interaction, G v (=fv G~, where * Member of the Scientific Research Career of the Consejo Nacional de Investigaciones Cientificas y T6cnicas of Argentina fv is the vector coupling constant and G B is the weak coupling constant for /~ decay), should not be renormalized, and thus should be constant from nucleus to nucleus; and (b) the coupling constant of the induced scalar (IS) interaction, fs, should be zero. Since the three independent comprehensive papers [24] on 0+-0 + /3 transitions were published in late 1975, new experimental improvements have enabled the experimental errors of the relevant measurable magnitudes to be significantly reduced.…”