New massive scalar or pseudo-scalar states with strong couplings to the top quark are predicted in numerous extensions of the Standard Model. These include models with an extended Higgs sector, such as Two-Higgs-Doublet Models (2HDMs). In this seminar, three recent searches for new scalar and pseudo-scalar particles with couplings to the top quark using the full Run-2 dataset are presented. Final states with two, three or four top quarks, targeting production of the heavy Higgs-like states via gluon-gluon fusion (gg→A/H), associated production with a top-quark (tA/H) or with a top-antitop-quark pair (tt̄A/H), as well as the t-channel production resulting in a same-sign top-quark pair are considered. The gg→A/H→tt̄ search takes into account interference with the SM process and provides the first full Run-2 search of this kind at the LHC. Searches in final states with more than two top quarks make use of neural networks, and provide the first collider result in a general 2HDM, with the heavy scalar featuring flavour changing couplings, including the first dedicated search featuring three top quarks.
Refreshments will be served at 10:30