CP-violating top quark couplings at future linear $e^+e^-$ colliders

TL;DR

Future linear electron-positron colliders like ILC and CLIC can significantly improve the detection of CP violation in top quark interactions, surpassing LHC capabilities, especially within two-Higgs-doublet models.

Contribution

This study provides detailed Monte Carlo analysis demonstrating the sensitivity of future colliders to CP-violating top quark couplings in specific beyond Standard Model scenarios.

Findings

High sensitivity to Higgs-induced CP violation at ILC and CLIC.

Potential to detect top quark dipole moments beyond HL-LHC capabilities.

Feasibility of measuring CP-violating form factors in top pair production.

Abstract

We study the potential of future lepton colliders to probe violation of the CP symmetry in the top quark sector. In certain extensions of the Standard Model, such as the two-Higgs-doublet model (2HDM), sizeable anomalous top quark dipole moments can arise, that may be revealed by a precise measurement of top quark pair production. We present results from detailed Monte Carlo studies for the ILC at 500~\GeV{} and CLIC at 380~\gev{} and use parton-level simulations to explore the potential of high-energy operation. We find that precise measurements in $e^+e^- \rightarrow t\bar{t}$ production with subsequent decay to lepton plus jets final states can provide sufficient sensitivity to detect Higgs-boson-induced CP violation in a viable two-Higgs-doublet model. The potential of a linear $e^+e^-$ collider to detect CP-violating electric and weak dipole form factors of the top quark exceeds the prospects of the HL-LHC by over an order of magnitude.