Search for dark matter in association with a top quark pair at sqrt(s)=13 TeV

A search is presented for an excess of events with large missing transverse momentum produced in association with top quarks in a data sample of proton-proton interactions at centre-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of $2.2\,\mathrm{fb}^{-1}$ collected by the CMS detector at the LHC in 2015. Results are interpreted in the context of dark matter production, and constraints are placed on the parameter space of simplified models.