Sensitivity of future-generation cosmic~microwave background experiments to detecting~dark matter-baryon interactions

In this work we investigate dark matter (DM) scattering with protons in the early Universe. We focus on velocity-dependent elastic scattering of DM particles with masses down to 100 MeV with protons. We forecast sensitivity of the next-generation cosmic microwave (CMB) background experiments to detecting DM-proton interactions using measurements of temperature, polarization, and lensing anisotropy. We find that they could deliver up to a factor of $\sim $ 23 improvement in constraining the DM-proton scattering cross-sections which scale quadratically with the relative particle velocity, up to a factor of $\sim $ 17 improvement for the cross-sections which~have quartic dependence on the relative velocity, and up to a factor of $\sim $ 53 improvement for the cross-sections of certain velocity-independent interactions.