Speaker
Description
There are several complementary searches for dark matter interacting with nuclei including underground direct detection experiments that use heavy nuclei, spherical detectors that make use of light nuclei, and cosmological probes that directly constrain dark matter-proton interactions. For dark matter with a mass $m_\chi > O(1)$ GeV, i.e., a weakly interacting massive particle (WIMP), the momentum transfer in WIMP-light nucleus scattering relevant for cosmological and spherical detector scenarios is bounded from above by a few MeV and thus much less than the pion mass. Therefore, we use pionless effective field theory (EFT), a theory in which the pion has been integrated out, to describe few-nucleon systems coupled to an external WIMP current. The EFT paradigm for nuclei interacting with external currents is ideal because it is systematically improvable and nearly model-independent; however, every operator in an EFT Lagrangian comes with a coupling that must be determined from data or nonperturbative calculations. In the absence of these determinations, theoretical constraints from other sources are necessary. Here, we use the spin-flavor symmetry of the baryon sector in large-$N_c$ quantum chromodynamics to constrain the relative sizes of the EFT couplings without recourse to data. We then explore the impact of these constraints on the WIMP-nucleus elastic scattering cross sections for several targets. Our results can interface with ongoing lattice and \textit{ab initio} calculations to guide the interpretation of experiments.
