A search for weakly interacting massive dark-matter particles 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 36.1fb-1 of proton–proton collision data recorded by the ATLAS experiment at 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 50GeV and assuming a dark-matter mass of 1GeV and unitary coupling. Constraints on colour-charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35GeV, mediator particles with mass below 1.1TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements.

Aaboud, M., Aad, G., Abbott, B., Abdinov, O., Abeloos, B., Abidi, S.H., et al. (2018). Search for dark matter produced in association with bottom or top quarks in √s=13 TeV pp collisions with the ATLAS detector. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS, 78(1) [10.1140/epjc/s10052-017-5486-1].

Search for dark matter produced in association with bottom or top quarks in √s=13 TeV pp collisions with the ATLAS detector

Ceradini, F.;Di Micco, B.;Di Nardo, R.;Orestano, D.;