# $Q_{\textrm{EC}}$-value determination for $^{21}$Na$\rightarrow^{21}$Ne and $^{23}$Mg$\rightarrow^{23}$Na mirror-nuclei decays using high-precision mass spectrometry with ISOLTRAP at ISOLDE/CERN

## TL;DR

This study uses high-precision mass spectrometry at ISOLDE/CERN to significantly improve the accuracy of $Q_{EC}$ values for specific mirror beta-decays, impacting fundamental tests of weak interactions.

## Contribution

It provides the most precise experimental $Q_{EC}$ values for $^{21}$Na and $^{23}$Mg decays, reducing uncertainties by a factor of five and revealing a deviation for $^{21}$Na.

## Key findings

- Enhanced precision of $Q_{EC}$ values by a factor of five.
- Detected a 2.3 sigma deviation in $^{21}$Na $Q_{EC}$ from previous data.
- Improved input data for testing weak interaction symmetries.

## Abstract

We report on high-precision $Q_{\textrm{EC}}$ values of the $^{21}$Na$\rightarrow^{21}$Ne and $^{23}$Mg$\rightarrow^{23}$Na mirror $\beta$-transitions from mass measurements with ISOLTRAP at ISOLDE/CERN. A precision of $\delta m/m = 9 \cdot 10^{-10}$ and $\delta m/m = 1.5 \cdot 10^{-9}$ was reached for the masses of $^{21}$Na and $^{23}$Mg, respectively. We reduce the uncertainty of the $Q_{\textrm{EC}}$ values by a factor five, making them the most precise experimental input data for the calculation of the corrected $\mathcal{F} t$-value of these mixed Fermi/Gamow-Teller transitions. For the $^{21}$Na$\rightarrow^{21}$Ne $Q_{\textrm{EC}}$ value, a $2.3 \sigma$ deviation from the literature $Q_{\textrm{EC}}$-value was found.