Ab Initio Structure Factors for Spin-Dependent Dark Matter Direct Detection.

Area of Science:

• Nuclear Physics
• Particle Physics
• Astrophysics

Background:

• Direct detection experiments search for Weakly Interacting Massive Particles (WIMPs) as dark matter candidates.
• Accurate theoretical predictions of WIMP-nucleus scattering are crucial for interpreting experimental results.
• Ab initio calculations provide a fundamental approach to nuclear structure and interactions.

Purpose of the Study:

• To compute precise structure factors for elastic spin-dependent WIMP scattering off nuclei relevant to dark matter detection.
• To establish a consistent theoretical framework for WIMP-nucleon currents, including two-body effects.
• To assess the impact of nuclear structure uncertainties on dark matter detection sensitivities.

Main Methods:

• Utilized ab initio calculations based on chiral effective field theory for nuclear interactions.
• Employed the in-medium similarity renormalization group (IMSRG) to derive effective nuclear Hamiltonians and operators.
• Incorporated natural orbitals and three-nucleon forces for basis-space convergence, especially in heavy nuclei.

Main Results:

• Presented converged structure factors for WIMP scattering off ^{19}F, ^{23}Na, ^{27}Al, ^{29}Si, ^{73}Ge, ^{127}I, and ^{129,131}Xe.
• Demonstrated consistency with previous calculations for most nuclei.
• Identified significant uncertainties in the structure factors for ^{127}I.

Conclusions:

• The study provides essential theoretical inputs for dark matter direct detection experiments.
• The developed ab initio framework offers a reliable method for calculating nuclear responses.
• Further theoretical and experimental efforts are needed to resolve uncertainties for specific nuclei like ^{127}I.