Chiral Effective Field Theory Calculations of Weak Transitions in Light Nuclei

We report Quantum Monte Carlo calculations of weak transitions in $A\le 10$ nuclei, based on the Norfolk two- and three-nucleon chiral interactions, and associated one- and two-body axial currents. We find that the contribution from two-body currents is at the $2$ - $3\mathrm{\%}$ level, with the exception of matrix elements entering the rates of ${}^8$Li, ${}^8$B, and ${}^8$He beta decays. These matrix elements are suppressed in impulse approximation based on the (leading order) Gamow Teller transition operator alone; two-body currents provide a $20$

• $30\mathrm{\%}$ correction, which is, however, insufficient to bring theory in agreement with experimental data. For the other transitions, the agreement with the data is satisfactory, and the results exhibit a negligible to mild model dependence when different combinations of Norfolk interactions are utilized to construct the nuclear wave functions. We report a complete study of two-body weak transition densities which reveals the expected universal behavior of two-body currents at short distances throughout the range of $A$=$3$ to $A$=$10$ systems considered here.