Electroweak and dark matter constraints on a Z′Z′ in models with a hidden valley

We consider current precision electroweak data, Z′Z′ searches and dark matter constraints and analyse their implications for an extension of the Standard Model (SM) that includes an extra U(1)′U(1)′ massive gauge boson and a particular hidden sector (“hidden valley”) with a confining (QCD-like) gauge group. The constraints on the Z′Z′ with arbitrary Z–Z′Z–Z′ kinetic mixing coming from direct searches and precision tests of the Standard Model are analysed and shown to lead to a lower limit of 800 GeV on its mass. Renormalisable interactions involving the Z′Z′ probe the physics of the hidden valley sector which contains a pseudoscalar dark matter candidate. We find that dark matter constraints place an upper bound on the mass of the Z′Z′ of O(10) TeVO(10) TeV. A TeV mass scale is needed for the hidden valley states, and the Sommerfeld factor for p-wave dark matter annihilation is found significantly to suppress the allowed parameter space of the model.