Search for heavy scalar or pseudoscalar states in $\mathrm{t}\bar{\mathrm{t}}$ events at CMS

A search for scalar or pseudoscalar states decaying to a top quark-antiquark pair ($\mathrm{t}\bar{\mathrm{t}}$), using $138{\mathrm{f}\mathrm{b}}^{-1}$ of pp collision data taken at $\sqrt{s}=13\mathrm{T}\mathrm{e}\mathrm{V}$ using the CMS detector, is presented. Events with one or two leptons are analyzed using the invariant $\mathrm{t}\bar{\mathrm{t}}$ mass ($m_{\mathrm{t}\bar{\mathrm{t}}}$) as well as angular and spin correlation observables. An excess in the data is observed for low values of $m_{\mathrm{t}\bar{\mathrm{t}}}$, preferring a pseudoscalar over a scalar hypothesis. It is interpreted in terms of a generic model of (pseudo)scalar boson production, as well as a simplified model of a $\mathrm{t}\bar{\mathrm{t}}$ bound state (${\eta }_{\mathrm{t}}$), yielding good agreement with the data. Moreover, limits on the couplings of additional (pseudo)scalar bosons to top quarks are set.