Probing a degenerate-scalar scenario in a pseudoscalar dark-matter model

We study a pseudoscalar dark-matter model arising from a complex singlet extension of the standard model (SM), and show that the dark-matter nucleon scattering is suppressed when two CP-even scalars are degenerate. In such a degenerate-scalar scenario we explore the model parameter space which satisfies constraints from the direct detection experiments and the relic density of dark matter. In addition, we discuss a possibility to verify such a scenario by using the recoil-mass technique at the International Linear Collider. We find that a pair of states separated by 0.2 GeV can be distinguished from the single SM-like Higgs state at 5s with an integrated luminosity of 2 ab(-1).

Automated summary

In this study, a pseudoscalar dark matter model from a complex singlet extension of the standard model is analyzed. It is found that dark-matter nucleon scattering is suppressed when two CP-even scalars are degenerate. The possibility of verifying this scenario using the recoil-mass technique at the International Linear Collider is also discussed.