Abstract: Two-body currents at zero momentum transfer and many-body correlations have been shown to be important ingredients for an accurate prediction of nuclei, e.g., solving the quenching puzzle in β-decay. To extract beyond standard model physics from other weakly interacting processes precise and accurate nuclear predictions are crucial. In processes, such as neutrinoless ββ decay and weakly interacting massive particles scattering off nuclei, etc., two-body currents at finite momentum transfer become an important contribution.

For a feasible calculation with two-body currents at finite momentum transfer in medium-mass and heavy nuclei, we include two-body currents via multipole decomposition and aim to investigate their effect on different observables. To solve the many-body problem we use the valence-space in-medium similarity renormalization group and apply chiral interactions.

Our first application is the most dominant M1 transition in 48Ca via the momentum-dependent transition form factor and the magnetic dipole transition strength B(M1). Different experiments found disagreeing B(M1) values. We find that our results favor larger values of B(M1) in agreement with a (γ,n) measurement and recent coupled-cluster calculations. For validation of our results, we investigate other observables in 48Ca, in particular the ground-state energy, the 1+ excitation energy of this dominant M1 transition and a GT strength, as well as a magnetic dipole transition strength B(M1) in another nucleus, 48Ti. Our predictions agree with the validating observables.