Scalar mass dependence of angular variables in $t\bar tφ$ production

In this paper we explore CP discrimination in the associated production of top-quark pairs ($t\bar{t}$) with a generic scalar boson ($\phi$) at the LHC. We probe the CP-sensitivity of several observables for a varying scalar boson mass and CP-number, either CP-even ($\phi=H$) or CP-odd ($\phi=A$), using dileptonic final states of the $t\bar{t}\phi$ system, with $\phi\rightarrow b\bar{b}$. We show that CP-searches are virtually impossible for $\phi$ boson masses above a few hundred GeV in this channel. A full phenomenological analysis was performed, using Standard Model background and signal events generated with MadGraph5 MC@NLO and reconstructed using a kinematic fit. The most sensitive CP-observables are used to compute Confidence Levels (CLs), as a function of luminosity, for the exclusion of different signal hypotheses with scalar and pseudoscalar boson masses that range from $m_\phi$ = 40 GeV up to 200 GeV. We finalize by analysing the impact of a measurement (or limit) of the CP-violating angle in the parameter space of a complex two-Higgs doublet model known as the C2HDM.DA, RC and RS are partially supported by the Portuguese Foundation for Science and Tech-nology (FCT) under Contracts no. UIDB/00618/2020, UIDP/00618/2020, PTDC/FIS-PAR/31000 /2017 and CERN/FIS-PAR/0002/2017, and the HARMONIA project undercontract UMO-2015/18/M/ ST2/00518. AO is partially supported by FCT, under the Contract CERN/FIS-PAR/0029/2019. DA is supported by ULisboa { BD2018.