%0 Journal Article %T Search for dark matter produced in association with a single top quark in root s=13 TeV pp collisions with the ATLAS detector %A ATLAS Collaboration (Aad, G. et al %A Aparisi Pozo, J. A. %A Bailey, A. J. %A Cabrera Urban, S. %A Cardillo, F. %A Castillo, F. L. %A Castillo Gimenez, V. %A Costa, M. J. %A Escobar, C. %A Estrada Pastor, O. %A Ferrer, A. %A Fiorini, L. %A Fullana Torregrosa, E. %A Fuster, J. %A Garcia, C. %A Garcia Navarro, J. E. %A Gonzalez de la Hoz, S. %A Gonzalvo Rodriguez, G. R. %A Guerrero Rojas, J. G. R. %A Higon-Rodriguez, E. %A Lacasta, C. %A Lozano Bahilo, J. J. %A Mamuzic, J. %A Marti-Garcia, S. %A Martinez Agullo, P. %A Mitsou, V. A. %A Moreno Llacer, M. %A Poveda, J. %A Prades IbaƱez, A. %A Rodriguez Bosca, S. %A Ruiz-Martinez, A. %A Sabatini, P. %A Salt, J. %A Santra, A. %A Sayago Galvan, I. %A Soldevila, U. %A Sanchez, J. %A Torro Pastor, E. %A Valero, A. %A Valls Ferrer, J. A. %A Villaplana Perez, M. %A Vos, M. %J European Physical Journal C %D 2021 %V 81 %N 10 %I Springer %@ 1434-6044 %G English %F ATLASCollaborationAad_etal2021 %O WOS:000702719500002 %O exported from refbase (https://references.ific.uv.es/refbase/show.php?record=4981), last updated on Fri, 15 Oct 2021 07:30:19 +0000 %X This paper presents a search for dark matter in the context of a two-Higgs-doublet model together with an additional pseudoscalar mediator, a, which decays into the dark-matter particles. Processes where the pseudoscalar mediator is produced in association with a single top quark in the 2HDM+a model are explored for the first time at the LHC. Several final states which include either one or two charged leptons (electrons or muons) and a significant amount of missing transverse momentum are considered. The analysis is based on proton-proton collision data collected with the ATLAS experiment at root s = 13 TeV during LHC Run 2 (2015-2018), corresponding to an integrated luminosity of 139 fb(-1). No significant excess above the Standard Model predictions is found. The results are expressed as 95% confidence-level limits on the parameters of the signal models considered. %R 10.1140/epjc/s10052-021-09566-y %U https://arxiv.org/abs/2011.09308 %U https://doi.org/10.1140/epjc/s10052-021-09566-y %P 860 - 37pp