A search for dark matter produced in association with a top quark pair is presented. The search is performed using 19.7 $mathrm{fb^{-1}}$ of proton-proton collisions recorded at a center of mass energy of 8 TeV with the CMS detector at the LHC. The s
ignature 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.
