Search for Dark Matter in final states with top quarks in CMS data

Searches for dark matter (DM) produced in association with a single top quark or a top quark pair in proton-proton collisions at $\sqrt{s}$ = 13 TeV are presented. The data corresponds to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$ recorded by the CMS detector at the CERN LHC in 2016. For the search with a single top quark, events with large missing transverse momentum and a hadronically decaying, Lorentz-boosted top quark are selected. Novel substructure techniques are utilized to identify the decay products of the top quark. No significant deviation from standard model (SM) expectation is observed. Limits are placed on the production of new heavy bosons coupling to DM particles. For a scenario with purely vector-like or purely axial-vector-like flavor changing neutral currents, mediator masses between 0.20 and 1.75 TeV are excluded at 95\pct confidence level, given a sufficiently small DM mass. Scalar resonances decaying into a top quark and a DM fermion are excluded for masses below 3.4 TeV, assuming a DM mass of 100 GeV. For searches with a top quark pair, final states with large missing transverse momentum and two oppositely charge leptons (electrons or muons) are selected. Several search strategies are described, including the use of multivariate analysis methods to improve background discrimination. No significant deviation from the SM is observed and limits are placed on the production of spin-0 mediators coupling to DM particles of mass 1 GeV. A scalar (pseudoscalar) mediator is excluded for masses below 100 (50) GeV.