We study an extension of the Standard Model (SM) in which two copies of the SM Higgs doublet are added to the scalar sector. These extra doublets do not develop a vacuum expectation value, hence, they are \textit{inert}. This essentially leads to a 3-Higgs Doublet Model (3HDM) with 2 inert and 1 active scalar doublets, which we denote as I(2+1)HDM. We allow for CP-violation in the \textit{inert} sector, where the lightest \textit{inert} state is protected from decaying to SM particles through the conservation of a Z2 symmetry, so that it is a Dark Matter (DM) candidate. For this scenario, we identify a smoking gun signature of dark CP-violation in the form of production thresholds of pairs of \textit{inert} neutral Higgs bosons at an e+e− collider.
@article{arxiv.1812.00820,
title = {Lepton collider signatures of dark CP violation},
author = {A. Cordero-Cid and J. Hernández-Sánchez and V. Keus and S. Moretti and D. Rojas and D. Sokołowska},
journal= {arXiv preprint arXiv:1812.00820},
year = {2020}
}