We report quantum Monte Carlo calculations of weak transitions in A 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% level, with the exception of matrix elements entering the rates of 8 Li, 8 B, and 8 He β decay. 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% 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.

We compute the matrix elements for elastic scattering of dark matter (DM) particles off light nuclei ( 2 H, 3 H, 3 He, 4 He and 6 Li) using quantum Monte Carlo methods. We focus on scalar-mediated DM-nucleus interactions and use scalar currents obtained to next-to-leading order in chiral effective theory. The nuclear ground states are obtained from a phenomenological nuclear Hamiltonian that includes the Argonne v18 two-body interaction and the three-body Urbana IX interaction. Within this approach, we study the impact of one-and two-body currents and discuss the size of nuclear uncertainties, including for the first time two-body effects in A = 4 and A = 6 systems. Our results provide the nuclear structure input needed to assess the sensitivity of future experimental searches of (light) dark matter using light nuclei, such as 3 He and 4 He.

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