Scalar mass dependence of angular variables in $t\bar{t}\ddot{I}•$ production

Abstract

In this paper we explore CP discrimination in the associated production of top-quark pairs ($t\bar{t}$) with a generic scalar boson ($\ddot{I}•$) at the LHC. We probe the CP-sensitivity of several observables for a varying scalar boson mass and CP-number, either CP-even ($\ddot{I}•=H$) or CP-odd ($\ddot{I}•=A$), using dileptonic final states of the $t\bar{t}\ddot{I}•$ system, with $\ddot{I}•\to b\bar{b}$. We show that CP-searches are virtually impossible for $\ddot{I}•$ 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 $m_{\ddot{I}}•$ = 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.

28 pages, 19 figures