Unitarity of the standard model at the Higgs resonance

Abstract We compute a unitarity bound for the Higgs mass using the one-loop corrected s-wave partial amplitude for ZLZL→ ZLZL scattering. We use the equivalence theorem and show that the Higgs mass has to be less than ≈ 600 GeV in order to save (perturbative) unitarity in the Higgs resonance region. We also discuss the validity of the perturbation expansion in the symmetry breaking sector.