Search for dark matter produced in association with bottom or top quarks in $\sqrt{s}$ = 13 TeV pp collisions with the ATLAS detector

TL;DR

This paper reports a search for dark matter produced with third-generation quarks at 13 TeV using ATLAS data, setting limits on mediator masses and cross-sections without observing a significant excess.

Contribution

It provides new constraints on spin-0 dark-matter mediators associated with bottom and top quarks using the ATLAS detector data from 2015-2016.

Findings

Excluded mediator masses below 50 GeV for certain models.

Set limits on production cross-sections up to 300 times the predicted rate.

Excluded mediator masses below 1.1 TeV for specific dark-matter models.

Abstract

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and missing transverse momentum are considered. The analysis uses 36.1 $fb^{-1}$ of proton-proton collision data recorded by the ATLAS experiment at $\sqrt{s}$ = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are interpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour-neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross-section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour-charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements.