Opening the Higgs Portal to Lepton-Flavoured Dark Matter

Abstract

We study a simplified model of lepton-flavoured complex scalar dark matter coupling to right-handed leptons and the Higgs boson. The model is set up in the Dark Minimal Flavour Violation framework. In contrast to previous studies of similar models we consider the most general case and do not a priori constrain the hierarchy of dark matter masses and couplings in any way. In the first part of the analysis we discuss the impact of Higgs portal interactions and the generalised mass hierarchy on the model's phenomenology. We find that they render new physics masses around the electroweak scale viable, thus qualifying this model to address the $(g-2)_\mu$ puzzle. After reviewing the current situation of the latter, we perform two combined analyses -- one in which $(g-2)_\mu$ allows for significant new physics effects and one in which it does not. We find that while the latter scenario allows for a larger range of new physics scales, both scenarios are equally viable.