Dark matter produced in association with top quark pair

A search for dark matter produced in association with a top quark pair is presented. The search is performed using 19.7 $\mathrm{f}{\mathrm{b}}^{-1}$ of proton-proton collisions recorded at a center of mass energy of 8 TeV with the CMS detector at the LHC. The signature investigated is top quark pairs in the semi-leptonic final state plus missing transverse energy. This work focuses in particular on dark matter production through scalar interaction where a proportionality to the quark mass is expected.