Hunting the dark Higgs

Abstract

We discuss a novel signature of dark matter production at the LHC resulting from the emission of an additional Higgs boson in the dark sector. The presence of such a dark Higgs boson is motivated simultaneously by the need to generate the masses of the particles in the dark sector and the possibility to relax constraints from the dark matter relic abundance by opening up a new annihilation channel. If the dark Higgs boson decays into Standard Model states via a small mixing with the Standard Model Higgs boson, one obtains characteristic large-radius jets in association with missing transverse momentum that can be used to efficiently discriminate signal from backgrounds. We present the sensitivities achievable in LHC searches for dark Higgs bosons with already collected data and demonstrate that such searches can probe large regions of parameter space that are inaccessible to conventional mono-jet or di-jet searches.

The pursuit of dark matter at colliders—an overview

“…A fairly recent development is the use of two Higgs doublet models (2HDM) [82,83,84], a class of simplified DM models for spin-0 mediators that are part of many BSM theories. The dark matter particle is coupled to a new spin 0 mediator and the coupling to the SM happens via the mixing to the Higgs boson or a (pseudo-)scalar partner of the Higgs boson [82].…”

“…Although it is necessary to introduce one additional parameter, these models are attractive due to their rich phenomenology. For example, if the spin-1 mediator decays visibly, one may obtain a mono-Z signature [156,157] while visible decays of the spin-0 mediator may lead to a signal from a 'dark Higgs boson' [83].…”

“…Feynman diagram for the production of DM χ in association with a SM Higgs boson arising from a Z − 2HDM model[83].…”

Enhancing dark matter annihilation rates with dark bremsstrahlung

“…More generally, models in which DM interactions are mediated by the exchange of only an axial-vector mediator are not gauge invariant. They require the addition of a dark Higgs to unitarize the longitudinal component of the gauge boson, and to give mass to both the gauge boson and DM [37][38][39][40][41][42]. Indeed, the simultaneous presence of both spin-1 and spin-0 mediators lead to new indirect detection phenomenology that does not arise in single mediator models [39][40][41].…”

“…For example, the radiation of photons from fermions in the FSR annihilation process χχ → f f γ is the analogue of the collider ISR mono-photon process f f → χχγ. Likewise, the ISR of a dark spin-0 or spin-1 field from the initial state χ in the χχ → f f φ or χχ → f f Z annihilation processes are then the analogue of the FSR mono-Z [80][81][82][83][84] or mono-dark Higgs [42] collider processes, respectively.…”