Dark matter searches at the LHC

The lack of suitable dark matter (DM) particle candidates in the Standard Model of particle physics (SM) hints at the need for a dark sector to be added to the model. One simplified dark matter model that does this type of extension is the DMsimp model.

In this work, we present a phenomenological study where we successfully perform the reconstruction of the top-anti-top system in the presence of a DM mediator, Y0, described by the DMsimp model, that couples to both the SM particles and the dark sector. Events involving Y0 production with a top-anti-top pair were generated for the Large Hadron Collider (LHC) using MadGraph5_aMC@NLO for four different mediator masses: 0 GeV, 1 GeV, 10 GeV and 125 GeV.

The reconstruction of the top-anti-top system is done with a kinematic fit for the dileptonic final states, without reconstructing the mediator. Lastly, confidence level exclusion limits are set on the mediator couplings with the top quarks for all generated mediator masses using CP angular observables to probe the CP-nature of the couplings.