Combination and summary of ATLAS dark matter searches using 139 fb-1 of √s = 13 TeV p p collision data and interpreted in a two-Higgs-doublet model with a pseudoscalar mediator

A combination of two searches for dark matter is presented, along with results from a wide range of experimental analyses that are interpreted in a common benchmark model: a Two-Higgs-Doublet Model with a pseudoscalar mediator. The analyses use up to 139 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy $\sqrt{s}=13$ TeV recorded with the ATLAS detector at the LHC between 2015-2018. The results from two searches targeting the $E_T^{\textrm{miss}}+Z(\ell\ell)$ and $E_T^{\textrm{miss}}+h(b\bar{b})$ signatures are statistically combined. The constraints of a wide range of additional experimental analyses, targeting final states with and without invisible particles, are evaluated and summarised alongside the combination in several interpretations within this model.