Precise measurements of half-lives and branching ratios for the ββ mirror transitions in the decay of 23Mg and 27Si

Half-lives and branching ratios for the two mirror ββ decays of 23Mg and 27Si have been measured at the University of Jyväskylä with the IGISOL facility. The results obtained, T1/2=11.303(3)T1/2=11.303(3) s and T1/2=4.112(2)T1/2=4.112(2) s for the half-lives of 23Mg and 27Si , respectively, are 7 and 8 times more precise than the averages of previous measurements. The values obtained for the super-allowed branching ratios of 23Mg and 27Si are B.R.=92.18(8)%B.R.=92.18(8)% and B.R.=99.74(2)%B.R.=99.74(2)% , respectively. The result for 23Mg is three times more precise than the average of the previous measurements, while for 27Si the precision has not been improved, the average of the previous…