Quantifying uncertainties in nuclear matrix elements for dark matter searches

In this contribution we report on quantification of theoretical uncertainties in nuclear matrix elements relevant for modeling dark matter and electro-weak interactions with nuclei. Recently we have developed a novel ab initio framework for computations of nuclear matrix elements and applied it in calculations of reaction rates for dark matter particles scattering off selected nuclear targets [1]. To evaluate the nuclear matrix elements we used nuclear wave functions computed within an ab initio many-body framework employing state-of-the-art nuclear Hamiltonians derived from chiral effective field theory. For the first time we have quantified the nuclear-physics uncertainties of the matrix elements that result from the remaining freedom in the construction of realistic nuclear interactions and their impact on physical observables. We found significant uncertainties especially for certain spin-dependent nuclear matrix elements. While our nuclear structure calculations have been performed with the no-core shell model method and applied in the context of dark matter searches, the approach can be generalized to other ab initio methods and extended to other sectors.