Probing sub-GeV Dark Matter-Baryon Scattering with Cosmological Observables

Understand

We derive new limits on the elastic scattering cross-section between baryons and dark matter using Cosmic Microwave Background data from the Planck satellite and measurements of the Lyman-alpha forest flux power spectrum from the Sloan Digital Sky Survey.

• Our analysis addresses generic cross sections of the form $\sigma\propto v^n$, where v is the dark matter-baryon relative velocity, allowing for constraints on the cross section independent of specific particle physics models.
• We include high-$\ell$ polarization data from Planck in our analysis, improving over previous constraints.
• We apply a more careful treatment of dark matter thermal evolution than previously done, allowing us to extend our constraints down to dark matter masses of $\sim$MeV.