  We use the current $t\bar t$ experimental analysis to look for Dark Matter
(DM) particles hidden in the final state. We present a phenomenological study
where we successfully perform the reconstruction of a $t\bar{t}$ system in the
presence of a scalar mediator $Y_0$, that couples to both Standard Model (SM)
and to DM particles. We use a \texttt{MadGraph5\_aMC@NLO} simplified DM model,
where signal samples of $pp \rightarrow t\bar{t}Y_0$ are generated at the Large
Hadron Collider (LHC) with both Charge-Parity (CP) -even and CP-odd couplings
of $Y_0$ to the top quarks. Different mass scales for the $Y_0$ mediator are
considered, from the low mass region ($\sim$ 0~GeV) to masses close to the
Higgs boson mass (125~GeV). The dileptonic final states of the $t\bar{t}$
system were used in our analysis. The reconstruction of the $t\bar{t}$ system
is done with a kinematic fit, without reconstructing the mediator. All relevant
SM backgrounds for the dileptonic $t\bar{t}$ search at the LHC are considered.
Furthermore, CP angular observables were used to probe the CP-nature of the
coupling between the mediator and top-quarks, which allowed to set confidence
level (CL) limits for those Yukawa couplings as a function of the mediator
mass.
