Search for dark matter particles produced in association with a top quark pair at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports a search for dark matter particles produced alongside top quark pairs in proton-proton collisions at 13 TeV, setting new constraints on scalar and pseudoscalar mediators with no observed excess.

Contribution

It provides the most stringent collider limits to date on scalar and pseudoscalar mediators for dark matter production in association with top quarks.

Findings

No significant excess over the standard model observed.

Sets new constraints on mediator-quark coupling strengths.

Provides the most stringent limits for low-mass mediators.

Abstract

A search is performed for dark matter particles produced in association with a top quark pair in proton-proton collisions at $\sqrt{s} =$ 13 TeV. The data correspond to an integrated luminosity of 35.9 fb$^{-1}$ recorded by the CMS detector at the LHC. No significant excess over the standard model expectation is observed. The results are interpreted using simplified models of dark matter production via spin-0 mediators that couple to dark matter particles and to standard model quarks, providing constraints on the coupling strength between the mediator and the quarks. These are the most stringent collider limits to date for scalar mediators, and the most stringent for pseudoscalar mediators at low masses.