Lower Bound on the Intermediate-Boson Mass

We report a search for the W boson via the production process ν_μ+Z→W⁺+μ^-+Z and decay process W⁺→μ⁺+ν_μ. We have set a firm lower bound on the mass of the W boson as a function of the branching fraction into leptons [B=(W→l+ν)(W→all)]. For example, we have determined that MW>4.4 GeV/c² (90% confidence limit) for $B=0.5$.