Ft asymmetry in A = 12 mirror decay to the 12C 4.4 MeV state

Abstract

The ratio of the Gamow-Teller beta-decay branches of 12B and 12N to the first excited state of 12C was measured accurately by means of the off-beam β-γ spectroscopy. The ratio of these branches was obtained as 12 N/ 12 B = 1.528 (27). This gives the mirror asymmetry [( ft) β +/( ft) β −]− 1 = 0.066 (18). The present value together with that for the ground-state decay is discussed in terms of the different radial overlapping.