Measurement of the Gamow-Teller Branching Ratio in the $\beta$-Decay of ${21}$Na
Abstract
The beta-decay branching ratio of the GT transition in 21Na to the first excited state in 21Ne has been measured. The value obtained of 4.93(20)% is in agreement with the most recent measurement and with the value adopted so far. This confirms that the branching ratio is not the source of discrepancy in a previous measurement of beta−v correlation coefficient which exhibited a 3sigma difference with respect to the Standard Model prediction.