Chiral Effective Field Theory calculations of weak transitions in light nuclei

We present {\it ab initio} calculations of weak transitions in $A\le 10$ nuclei--including beta decays of $^{6}$He, $^{8}$Li, $^{8}$B, $^{8}$He, and $^{10}$C and electron-capture in $^{7}$Be--using Variational and Green's Function Monte Carlo methods. Calculations of matrix elements employ the Norfolk potential, a high-quality local chiral interaction containing two- ($NN$) and three-body ($3N$) forces, and consistent one- and two-body axial currents. We investigate the sensitivity of the matrix elements to choices of different cutoffs and different strategies to constrain the $NN$ and $3N$ potentials. For $A < 10$, the inclusion of two-body axial currents results in a small additive contribution to the one-body matrix element for these various choices, except for in the $A=8$ systems where we find a significant contribution from two-body axial currents. In the case of $A=10$, we find that our results vary depending on the adopted nuclear interactions. In addition, we present calculations of one- and two-body transition densities. These studies provide a validation of nuclear many-body correlations and currents entering {\it ab initio} calculations and impact studies of neutrinoless double beta decay and searches for beyond standard model physics.