Nuclear \sigma-terms and Scalar-Isoscalar WIMP-Nucleus Interactions from Lattice QCD

TL;DR

This study uses lattice QCD to estimate nuclear -terms for light nuclei, finding minimal deviation from single-nucleon estimates and suggesting limited impact of meson-exchange currents on WIMP-nucleus interaction uncertainties.

Contribution

It provides the first lattice QCD-based estimates of nuclear -terms for light nuclei, challenging the expected enhancement from meson-exchange currents.

Findings

Nuclear -terms deviate only slightly from single-nucleon estimates.

Meson-exchange currents do not significantly increase WIMP-nucleus interaction uncertainties.

Lattice QCD results suggest minimal impact of MECs on scalar-isoscalar WIMP detection.

Abstract

It has been argued that the leading scalar-isoscalar WIMP-nucleus interactions receive parametrically enhanced contributions in the context of nuclear effective field theories. These contributions arise from meson-exchange currents (MECs) and potentially modify the impulse approximation estimates of these interactions by 10--60%. We point out that these MECs also contribute to the quark mass dependence of nuclear binding energies, that is, nuclear \sigma-terms. In this work, we use recent lattice QCD calculations of the binding energies of the deuteron, He-3 and He-4 at pion masses near 500 MeV and 800 MeV, combined with the experimentally determined binding energies at the physical point, to provide approximate determinations of the \sigma-terms for these light nuclei. For each nucleus, we find that the deviation of the corresponding nuclear \sigma-term from the single-nucleon estimate is at the few percent level, in conflict with the conjectured enhancement. As a consequence, lattice QCD calculations currently indicate that the cross sections for scalar-isoscalar WIMP-nucleus interactions arising from fundamental WIMP interactions with quarks do not suffer from significant uncertainties due to enhanced meson-exchange currents.