Abstract
We discuss universal signals of consistent models of pseudoscalar mediators for collider searches for Dark Matter. Keeping only the degrees of freedom that can not be decoupled due to consistency conditions, we present a universality class of simplified models with pseudoscalar mediators and renormalizable couplings to Standard Model fields. We compute stability and perturbativity constraints, constraints from electroweak precision measurements, collider searches for new heavy particles as well as constraints from relic density measurements and indirect detection experiments searching for signals of Dark Matter annihilation into photons. We find that the mono-Z final state is the strongest, universal signal of this class of models, with additional signatures present in the different ultraviolet completions that can be used to distinguish between them.
Highlights
Constrain spin-0 mediators with scalar couplings to SM fermions, whereas spin-0 mediators with pseudoscalar couplings lead to velocity suppressed couplings between nuclei and dark matter [17]
We work out signals common to a large class of gauge invariant models, by exploring a consistent, gauge invariant effective field theory (EFT) in which only those additional mediators that cannot be decoupled are kept as explicit degrees of freedom
We establish the parameter space in which the dark matter candidate can explain the observed relic density in this class of models, compute constraints from direct detection experiments taking the additional mediators into account and provide a strategy for collider searches for this well-motivated region of parameter space
Summary
Gauge invariant models of pseudoscalars imply new particles charged under the SM gauge symmetries. If the pseudoscalar mediator is a SM singlet, the couplings between SU(2)L. H denotes the SU(2)L doublet Higgs boson and the scale Λ is typically associated with the mass of additional color-charged fermions or additional inert scalar doublets [26] Searches for these additional particles put strong constraints on the mass scale Λ, which leads to a suppressed production cross section of the pseudoscalar a at colliders. As in extended doublet-singlet dark matter models [29], encompassing the Bino-Higgsino limit of the minimal supersymmetric Standard Model While these UV completions predict very different, model-specific signatures that allow to differentiate between them, the focus of this work is on universal signals that arise in all pseudoscalar mediator models which lead to the EFT (2.2). The parameter space of the effective theory described in the previous section is constrained by observables, independent of the couplings to dark matter, such as flavour and electroweak precision observables, Higgs coupling measurements, and searches for the additional scalars decaying in SM final states. We discuss the corresponding constraints on the parameter space
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