Searching for Dark Matter in top quark production with the CMS experiment

A search for Dark Matter (DM) produced in association with a top quark pair using $137 \mathrm{fb}^{-1}$ of 13 TeV pp collision data collected with the CMS experiment at the Large Hadron Collider (LHC) is presented. No excess was observed, and limits were set on the nominal cross-section for scalar mediators up to 420 GeV, and pseudoscalar mediators up to 400 GeV. Further improvements for an in-progress analysis which also targets DM produced in association with a single top quark are also shown, including the use of neural networks to improve the sensitivity.