Fermion dark matter with scalar triplet at direct and collider searches

Abstract

Fermion dark matter (DM) as an admixture of additional singlet and doublet vectorlike fermions provides an attractive and allowed framework by relic density and direct search constraints within TeV scale, although limited by its discovery potential at the Large Hadron Collider (LHC) excepting for a displaced vertex signature of charged vectorlike lepton. An extension of the model with the scalar triplet can yield neutrino masses and provide some cushion to the direct search constraint of the DM through pseudo-Dirac mass splitting. This in turn, allows the model to live in a larger region of the parameter space and open the door for detection at LHC through hadronically quiet dilepton channel, even if slightly. We also note an interesting consequence to the hadronically quiet four lepton signal produced by the doubly charged scalar belonging to the triplet, in the presence of additional vectorlike fermions as in our model. The model however can see an early discovery at International Linear Collider (ILC) without too much of fine-tuning. The complementarity of LHC, ILC and direct search prospect of this framework is studied in this paper.