$^{28}$Al Half-life Measurement and the negative mirror asymmetry between the $^{28}$Al($\beta^-$)$^{28m}$Si and $^{28}$P($\beta^+$)$^{28m}$Si decays

TL;DR

This paper reports the first measurement of the $^{28}$Al half-life, providing data to better understand mirror asymmetry in nuclear beta decay, which tests the Standard Model and probes for new physics.

Contribution

The study presents the first half-life measurement of $^{28}$Al using a radioactive ion beam, refining the data used to analyze mirror asymmetry and its implications for fundamental physics.

Findings

Measured $^{28}$Al half-life as 134.432(34) seconds.

Found the mirror asymmetry parameter to be -3.5(10)%.

Results are consistent with most previous data, except one.

Abstract

In the past, the mirror asymmetry parameter has been proposed as a probing mechanism for the presence of beyond the Standard Model second-class currents in nuclear beta decay transitions. However, this was hindered by large uncertainties in the required nuclear structure correction terms. Recently, a new calculation of these corrections attempted, but could not fully explain the negative mirror asymmetry between the $^{28}$Al($\beta^-$)$^{28m}$Si and $^{28}$P($\beta^+$)$^{28m}$Si decays. To put the mirror asymmetry parameter on a more solid footing, the half-life of $^{28}$Al was measured for the first time using a radioactive ion beam at the Nuclear Science Laboratory of the University of Notre Dame. The new result, $t_{1/2}=$134.432(34) s, is consistent with most of the past data except for one highly discrepant measurement. The new mirror asymmetry parameter of -3.5(10)$\%$ obtained still does not agree with nuclear structure calculations.