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⁺, Ï„^−τ⁺, qqÌ…, W^−W⁺, and ZH at √s = 3 TeV  (â„’ = 2ab^−1) and √s = 10 TeV (â„’ = 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.