Search for BSM physics in final state with a top quark and invisible particles at CMS experiment.

A signature-based study involving top quarks produced in association with invisible particles using proton-proton collisions at $\sqrt{s}=13$ TeV with CMS data is presented. The final state involves a single top quark decaying hadronically, and either Dark Matter (DM) particles or neutrinos, that can be indirectly detected through the missing transverse momentum of the event. Of the above two scenarios, the first one is based on a model that predicts a privileged interaction between top quarks and DM particles through a new boson $\phi$, the second one on a model including a Vector-Like Quark (VLQ) $T$ that decays to a top quark plus a $Z$ boson. The contribution focuses on the reconstruction of top quarks through hadronic jets. The reconstruction can be performed through three different topologies, making use of jets reconstructed by anti-$k_t$ algorithms with different radii. Machine Learning algorithms have been trained on the three different kinds of reconstructed top quarks to improve signal efficiency and background rejection. Preliminary results will be presented for different mass hypotheses of $\phi$ boson, in the first scenario, and of VLQ $T$, in the second one.