Overview on low mass scalars at $e^+e^-$ facilities -- theory

Abstract

I give a short summary of scenarios with new physics scalars that could be investigated at future $e^+e^-$ colliders. I concentrate on cases where at least one of the additional scalar has a mass below 125 GeV, and discuss models where this could be realized. In general, there are quite a few additional new physics scenarios and signatures that are still allowed by current constraints and should be investigated in more detail at future $e^+e^-$ machines. Most of the material presented here has already been discussed in arXiv:2307.15962, and I therefore try to focus on novel developments since then.