Speaker
Description
We present the first ab-initio calculations of the structure factors for elastic spin-dependent WIMP scattering off $^{19}$F, $^{27}$Al, $^{23}$Na, $^{27}$Al, $^{29}$Si, $^{73}$Ge, $^{127}$I and $^{129,131}$Xe. A set of established two- (NN) and three-nucleon (3N) interactions derived from chiral effective field theory (EFT) are used for nuclear interaction, including N$^3$LO-level NN + N$^2$LO-level 3N, N$^4$LO-level NN + N$^2$LO-level 3N, and N$^2$LO-level NN+3N with the $\rm{\Delta}$(1232)-isobar degrees of freedom. Within the same chiral EFT framework, we employ corresponding WIMP-nucleus currents at the one-body level and also include the effects from axial-vector two-body currents. We then apply the ab-initio in-medium similarity renormalization group to construct valence-space Hamiltonians and consistently transformed operators of nuclear responses. By combining the newly developed frameworks, natural orbitals and expressing the 3N force with a very large basis size, we obtain basis-space converged structure factors in heavy nuclei. This work paves the path toward a true first-principles calculation of the structure factor for WIMP scattering in all nuclei relevant for ongoing searches. All results are publicly available in a Jupyter notebook.
