DarkELF: A python package for dark matter scattering in dielectric targets

Abstract: We present a python package to calculate interaction rates of light dark matter in dielectric materials, including screening effects. The full response of the material is parametrized in the terms of the energy loss function (ELF) of material, which darkELF converts into differential scattering rates for both direct dark matter electron scattering and through the Migdal effect. In addition, darkELF can calculate the rate to produce phonons from sub-MeV dark matter scattering via the dark photon mediator, as well as the absorption rate for dark matter comprised of dark photons. The package includes precomputed ELFs for Al, $\mathrm{Al}_2\mathrm{O}_3$, GaAs, GaN, Ge, Si, $\mathrm{SiO}_2$, and ZnS, and allows the user to easily add their own ELF extractions for arbitrary materials.