Abstract
An electroweak multiplet stable due to a new global symmetry is a simple and well-motivated candidate for thermal dark matter. We study how direct searches at a future linear collider, such as the proposed CLIC, can constrain scalar and fermion triplets, quintets and septets, as well as a fermion doublet. The phenomenology is highly sensitive to charged state lifetimes and thus the mass splitting between the members of the multiplet. We include both radiative corrections and the effect of non-renormalisable operators on this splitting. In order to explore the full range of charged state lifetimes, we consider signals including long-lived charged particles, disappearing tracks, and monophotons. By combining the different searches we find discovery and exclusion contours in the mass-lifetime plane. In particular, when the mass splitting is generated purely through radiative corrections, we can exclude the pure-Higgsino doublet below 310 GeV, the pure-wino triplet below 775 GeV, and the minimal dark matter fermion quintet below 1025 GeV. The scenario where the thermal relic abundance of a Higgsino accounts for the whole dark matter of the Universe can be excluded if the mass splitting between the charged and neutral states is less than 230 MeV. Finally, we discuss possible improvements to these limits by using associated hard leptons to idenify the soft visible decay products of the charged members of the dark matter multiplet.
Highlights
We focus on Compact Linear Collider (CLIC) since it has progressed to the stage of a conceptual design report (CDR) [5]; the question of the reach of the more optimistic muon colliders is one we leave to future work
The phenomenology is set by the charged state lifetimes, which in turn are determined by the mass splitting
CLIC has the highest centre of mass energy among current proposals for linear colliders, and so we focus on this experiment
Summary
√ mass energy, which motivates us to consider the proposal with the largest s = 3 TeV, the Compact Linear Collider (CLIC) [5]. Muon colliders are an alternative speculative proposal for high-energy lepton colliders. A range of possible centre of mass energies have been proposed, from those comparable to. The reach of a muon collider with comparable energy would probably be similar, since the signal processes we consider here are independent of initial lepton flavour. The phenomenology is set by the charged state lifetimes, which in turn are determined by the mass splitting. This leads us to consider three distinct phases, in order of increasing ∆m1:
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
