Precise half-life measurement of the superallowed mixed-miror decaying $^{15}$O*

The Standard Model encapsulates our current understanding of matter and interactions in the universe, however there are some known shortcomings which provide a strong incentive to probe explicit experimental evidence of new physics. One such test lies in investigating the unitarity of the CKM matrix. The current limit is provided by a determination of the $V_{ud}$ matrix element, which relies on measurements of half-lives, branching ratios, and Q-values for the ensemble of $0^+\rightarrow0^+$ decays in order to extract $\mathcal{F}$$t$ values. This calculation, however, also requires knowledge of theoretical corrections, so it is ambitious to confirm the result with another ensemble such as T=1/2 mixed-mirror decays. Aligning with these interests, the half-life of $^{15}$O was measured using the $\beta$-Counting Station at the Nuclear Science Laboratory of the University of Notre Dame. Prior to this measurement the uncertainty of the $\mathcal{F}$$t$ value was dominated by the lifetime. The measurement, along with its impact of the $\mathcal{F}$$t$ value will be presented.