Abstract
We study the lepton portal dark matter (DM) model in which the relic abundance is determined by the portal coupling among the Majorana fermion DM candidate χ, the singlet charged scalar mediator S± and the Standard Model (SM) right-handed lepton. The direct and indirect searches are not sensitive to this model. This article studies the lepton portal coupling as well as the scalar portal coupling (between S± and SM Higgs boson), as the latter is generally allowed in the Lagrangian. The inclusion of scalar portal coupling not only significantly enhances the LHC reach via the gg → h* → S+S− process, but also provides a few novel signal channels, such as the exotic decays and coupling devi- ations of the Higgs boson, offering new opportunities to probe the model. In addition, we also study the Drell-Yan production of S+S− at future lepton colliders, and find out that the scenario where one S± is off-shell can be used to measure the lepton portal coupling directly. In particular, we are interested in the possibility that the scalar potential triggers a first-order phase transition and hence provides the stochastic gravitational wave (GW) signals. In this case, the terrestrial collider experiments and space-based GW detectors serve as complementary approaches to probe the model.
Highlights
The results from direct detection [4], indirect detection [5] and collider searches [6] have been pushing more and more stringent bounds on WIMPs, there is still room for this scenario
We study the lepton portal dark matter (DM) model in which the relic abundance is determined by the portal coupling among the Majorana fermion DM candidate χ, the singlet charged scalar mediator S± and the Standard Model (SM) right-handed lepton
Various terrestrial searches are investigated, including the S+S− production, the exotic decay and coupling deviations of the Higgs boson at the LHC and future e+e− colliders, together with lepton (g − 2) searches to constrain the two portal couplings in this model. The scenario that this model provides the right DM relic abundance and at the same time triggers a firstorder phase transition (FOPT) is considered in section 4, in which we show that detectable gravitational wave (GW) signals suggest a large Higgs portal coupling
Summary
The model contains two new fields: the Majorana DM candidate χ, which is a gauge singlet; and the complex scalar mediator S, which is an SU(2)L singlet with hypercharge −1. We require S couple to one generation of lepton at a time to avoid lepton flavor violation. Since χ is a Majorana fermion, its dimension-five magnetic dipole operator vanishes It leaves the dimension-six operator as the leading contribution, which can be matched to the electromagnetic anapole moment of DM. This receives additional suppression from DM velocity square, so that it is difficult to detect from the direct detection experiments [23].1. We conclude that the lepton portal DM with Majorana DM has negligible signal in indirect and direct searches, and is only subject to the constraints from the thermal relic abundance and collider searches This receives additional suppression from DM velocity square, so that it is difficult to detect from the direct detection experiments [23].1 As a result, we conclude that the lepton portal DM with Majorana DM has negligible signal in indirect and direct searches, and is only subject to the constraints from the thermal relic abundance and collider searches
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
