Unraveling the sensitivity of a future muon collider to dark Z resonances

Abstract

We explore the sensitivity of a future muon collider to dark Z decaying to e⁻e⁺, μ⁻μ⁺, τ⁻τ⁺, qq̅, W⁻W⁺, and ZH at √s = 3 TeV  (ℒ = 2ab⁻¹) and √s = 10 TeV (ℒ = 10 ab⁻¹) centre-of-mass energies and projected integrated luminosities. We found that without putting explicit cuts on the background, the muon collider is mostly sensitive in the production mode channel where dark Z decays to W⁻W⁺ due to longitudinal W^± contributions to the signal cross section. This corresponds to the branching ratio where mass mixing dominates over kinetic mixing. Thus, the muon collider can effectively distinguish dark Z from a dark photon.