Consideration of core polarization, meson exchange, and relativistic corrections gives a satisfactory, quantitative understanding of mirror Gamow-Teller $\beta$-transitions in $A=3, 15, 17, 39, \mathrm{and} 41$ nuclei.

• Received 6 November 1978

DOI:https://doi.org/10.1103/PhysRevLett.42.51