Searching for GeV-scale Majorana Dark Matter: inter spem et metum

Abstract

We suggest a minimal model for GeV-scale Majorana Dark Matter (DM) coupled to the standard model lepton sector via a charged scalar singlet. We show that there is an anti-correlation between the spin-independent DM-Nucleus scattering cross-section (${\sigma }_{\mathrm{SI}}$) and the DM relic density for parameters values allowed by various theoretical and experimental constraints. Moreover, we find that even when DM couplings are of order unity, ${\sigma }_{\mathrm{SI}}$ is below the current experimental bound but above the neutrino floor. Furthermore, we show that the considered model can be probed at high-energy lepton colliders using e.g. the mono-Higgs production and same-sign charged Higgs pair production.

Comments: 29 pages, 9 figures and 4 Tables. Added section about LHC constraints on the model, improved discussion on the implications at lepton colliders. Comments are welcome!