Search for a new $Z'$ gauge boson via the $pp → W±(*) → Z' μ± ν → μ±μ∓μ±ν$ process in $pp$ collisions at √s=13 TeV with the ATLAS detector

A search for a new $Z'$ gauge boson predicted by Lμ-Lτ models, based on charged-current Drell-Yan production, pp → W±(*) → Z' μ± ν → μ±μ∓μ±ν, is presented. The data sample used corresponds to an integrated luminosity of 140 fb⁻¹ of proton-proton collisions at √s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The search examines a final state of 3μ plus large missing transverse momentum. Upper limits are set on the $Z'$ production cross-section times branching ratio in the mass range of 5-81 GeV. After combining with the previous $Z'$ search using the neutral-current Drell-Yan production with a 4μ final state, the most stringent exclusion limits to date are achieved in the parameter space of the $Z'$ coupling strength and mass.