Fermi nuclear matrix element of allowed isospin-hindered positron decay ofCo56

Abstract

The experimental measurement of the asymmetry parameter of the P+ decay from the 4+ ground state of Co to the 2.085 MeV 4+ state of ' Fe not only yields a value for the Fermi nuclear matrix element MF, but also has significant Fermi-Gamow-Teller mixing and is of interest for a timereversal invariance test of the weak interaction. To date, nine such measurements have been made and the values of the MF fall into two groups: M~-10 ' and MF -(3-5)X 10 . Our theoretical calculation using the Nilsson model and a one-body spheroidal Coulomb potential yields Mr=2. 3X10 for p=0. 1 and Mr --6X10 for p=0. 2, which are in reasonable agreement with the experimental values of MF -(3-5)X 10

The Fermi to Gamow-Teller mixing ratio of the? + decay of52Mn and time-reversal invariance

“…A number of theoretical calculations [12][13][14][15][16][17] Recently [19][20][21][22], we have used the Nilsson model with a one-body spheroidal Coulomb potential to obtain the MF of a number of transitions. As the results show reasonably good agreement between theory and experiment, we shall use the same approach.…”

“…The value of MeT can be obtained from the following relation [22]: =Cv] / 2ft (superallowed) 1 IMGTI CA 1/ ft(decay under study) ]/l+y2" (8) Owing to the smallest of the experimental value of y, we shall obtain essentially the same value of MeT irrespective of whichever experimental value I-1-10] of y we use.…”