R.J. Blin-Stoyle

Coupling constants and electromagnetic radiative corrections in beta-decay and the mass of the intermediate vector boson

Abstract Effective beta-decay coupling constants G′v and G′A are defined which include renomalizing effects due to the electromagnetic interaction. Analysis of recent beta-decay data then gives G′v = 1.4150 ± 0.0011 × 10−49 erg · cm3 and |G′ A G′ v | = 1.226 ± 0.011 . It is concluded that only those theories of electromagnetic radiative corrections which take account of a very heavy intermediate vector boson are able to reconcile the values of G′v, Gμ and the Cabibbo angle determined from polar vector strangeness changing semi-leptonie decays.

Evidence for G parity non-invariance from the β-decays of B12 and N12

Abstract All possible second-forbidden, electromagnetic and other charge-dependent effects which could account for the difference in the ft values for the β-decays of B 12 and N 12 are considered. It is concluded that it is highly unlikely that such effects fully account for the difference, and it is suggested that there is, therefore, some evifence for the β-decay interaction being non-invariant under the transformation G .

Exchange corrections to the allowed β-decay of the A = 15, 17, 39 and 41 mirror nuclei

Abstract A calculation is made of the mesonic exchange corrections to the allowed axial vector mirror β-decays 15 O → 15 N , 17 F → 17 O , 39 Ca → 39 K and 41 Sc → 41 Ca . It is found that the corrections are significantly state dependent and can be both positive and negative.

Fermi functions for superallowed beta decays and the value of GV

Abstract To extract the polar vector beta-decay coupling constant G V from the data on 0 + → 0 + superallowed transitions, accurate values of the Fermi function are needed. We report the details and the results of a numerical evaluation of the relevant Fermi functions. Both the finite size charge distribution of the nucleus and the screening effect due to the atomic electrons are taken into account. The G V (or alternatively the ft values) calculated with these Fermi functions agree very well with earlier results for 10 C, 14 O, 26m Al and 34 Cl but not for 42 Sc, 46 Vn, 50 Mn and 54 Co. The probable reason for the disagreement is given, and the implications of the results are discussed.

The charge dependence of nuclear forces and ΔT = ±1 Fermi transitions

Abstract Measurements of the β-γ circular polarization in the ΔT = ±1 decays of Na24, Ar41, Sc44 and Mn52 enable experimental values of the Fermi matrix elements MF calculated on the jj-coupled shell model and including a short-range charge dependent internucleon potential in addition to the usual Coulomb potential. The results are consistent with a few per cent charge dependence of nuclear forces, and with the conserved vector current theory of weak interactions.

Renormalization of the axial-vector coupling constant in β-decay

Abstract Relationships are established between different theoretical approaches which attempt to account for the quenching of the axial-vector β-decay coupling constant g A . It is concluded that it is probably not meaningful to attribute the quenching observed in light nuclei to any one particular mechanism.

A theoretical study of T-violation in 192Pt

Abstract A theoretical study is made of T -violation in nucleary-decay in terms of a phenomenological T -violating internucleon potential. The results are applied to experimental data obtained for γ-decay in 192 Pt and an upper limit is derived for the strength of the T -violating potential.

Present status of the conserved vector current theory

Abstract A critical survey is given of the theoretical implications of the various experiments which are normally quoted as favouring the conserved vector current theory. It is concluded that although experiments are in general consistent with the theory, it is not clear that they are inconsistent with a theory in which the polar vector current is not conserved.

Parity impurities due to a static PNC potential

Abstract It is shown that unlike the σ·ϱ single-particle, velocity-dependent potential, a static parity non-conserving (PNC) potential can lead to both electric as well as magnetic irregular transitions even for a spin-independent nuclear Hamiltonian. Specific calculations are made of the circular polarization P to be expected in the case of the 480 keV γ-transition in 181 Ta due to a static PNC potential. It is found that P ≈ −0.7 · 10 −4 .

The beta decay of 24Na: Fermi nuclear matrix element and charge dependence of nuclear forces

Abstract It is shown that the use of Nilsson wave functions enables the magnitude of the Fermi matrix element for the 24 Na (J=4 + , T=1) → 24 Mg (J=4) + , T=0) β-decay to be accounted for in terms of a charge dependence of nuclear forces consistent with that deduced from experimental data.