Ultra-High Precision Half-Life Measurement for the Superallowed $\beta^+$ Emitter $^{26}$Al$^m$

The calculated nuclear structure dependent correction for $^{26}$Al$^m$ ($\delta_{C}-\delta_{NS} = 0.305(27)\%$ [1]) is smaller by nearly a factor of two than the other twelve precision superallowed cases, making it an ideal case to pursue a reduction in the experimental errors contributing to the $\mathcal{F}${\em t} value. An ultra-high precision half-life measurement for the superallowed $\beta^+$ emitter $^{26}$Al$^m$ has been made using a 4$\pi$ continuous gas flow proportional counter as part of an ongoing experimental program in superallowed Fermi $\beta$ decay studies at the Isotope Separator and Accelerator (ISAC) facility at TRIUMF in Vancouver, Canada, which delivered a beam of $\sim 10^5$ $^{26}$Al$^m$/s in October 2007. With a statistical precision of $\sim0.008\%$, the present work represents the single most precise measurement of any superallowed half-life to date. \\ \newline [1] I.S.~Towner and J.C.~Hardy, Phys. Rev. C {\bf 77}, 025501 (2008).