Precision half-life measurement of ${}^{25}\mathrm{Al}$

A new precision half-life measurement of ${}^{25}\mathrm{Al}$ was conducted using the TwinSol $\beta$-counting station at the University of Notre Dame. The new measured value of $t_{1/2}^{\mathrm{new}}=7.1657\left(24\right)$ s is in good agreement with the most recent measurement, while being 3 times more precise. Using these new measurements, an evaluation of the ${}^{25}\mathrm{Al}$ half-life has been performed, leading to an average half-life of $t_{1/2}^{\mathrm{world}}=7.1665\left(26\right)$ s, which is 5 times more precise than it's predecessor and has a more satisfactory Birge ratio of 1.1. To aid in future measurements of correlation parameters, a new Fermi to Gamow-Teller mixing ratio $\rho$ and correlation parameters for this mixed transition have been calculated assuming the standard model validity using the new world half-life.

Figure 1

Summed $\beta$-decay curve of all 32 runs. Below are the residuals of the fit divided by the square root of the number of ions in a given bin $N$. The data have been rebinned to 500 bins.

Figure 2

half-life ${}^{25}\mathrm{Al}$ fits from Monte Carlo simulated data for various numbers of bins. The blue circles indicate data simulated with a typical background while the orange squares show data simulated with a low background. The central orange line is the true value and the two red outer lines indicate the uncertainty on the weighted average from this work.

Figure 3

Fitted half-lives for the total summed data with leading bins removed and the fit performed on the remaining bins. Up to 15 half-lives were removed. The two red horizontal lines indicate the uncertainty on the summed fit without any bin removal.

Figure 4

Plot of the half-lives of ${}^{25}\mathrm{Al}$ vs the beam current for each run. The point color notates the discriminator voltage and the point shape notates the photomultiplier tube voltage for each run. The red double lines represent the $1\sigma$ uncertainty on the weighted average of the individual half-lives.

Figure 5

half-lives ${}^{25}\mathrm{Al}$ [30] considered in the evaluation of the new world value. The triangle points colored red were included in the old world value but were removed from our evaluation. The scaled uncertainty on the overall ${}^{25}\mathrm{Al}$ half-life of 7.1665(26) s is represented by the red band.

Figure 6

The relative uncertainty for quantities needed to calculate $\mathcal{F}{t}^{\mathrm{mirror}}$. The $f_v$ value was calculated from the $Q_{\mathrm{EC}}$ value.