Precise Lifetime Measurement of $^{37}$K

To determine the correlation parameters of the $\beta $ decay of transitions between isobaric analogue states, the \textit{ft} value is needed to determine $\rho $, the ratio of Gamow-Teller to Fermi matrix elements. A recent review of all $T = \frac{1}{2} \beta$ mirror decays [1] indicates that $^{37}$K is one of the best candidates for testing the Standard Model. The \textit{ft} value is currently limited by the 0.6{\%} uncertainty in the lifetime. In order to make Standard Model predictions of the correlation parameters negligible compared to planned experiments, we have performed a precision lifetime measurement of $^{37}$K. We used the MARS separator for producing a secondary beam of $^{37}$K with a purity of 98.5{\%}. We implanted the activity in an aluminized-Mylar tape that, as part of a fast-tape drive system, quickly transported the sample to a well shielded location, stopping it in the centre of a 4$\pi $ proportional gas counter. The recorded data was separated into 25 runs, each characterized by a different combination of detector high voltages, discriminator thresholds and dominant dead-time settings. An overview of the experiment and results will be presented. \\[4pt] [1] O. Naviliat-Cuncic and N. Severijns, Phys. Rev. Lett. \textbf{102}, 142302 (2009)