One-loop perturbative unitarity and the Higgs-boson mass: A new approach

We reexamine the unitarity constraints on the high-energy scattering of longitudinal W ’s and Z’s and Higgs bosons in the standard model including one-loop corrections, and make an Argand-diagram analysis of the j=0 scattering amplitudes. We find that the theory is approximately unitary and weakly interacting at O(${\lambda }^2$) for Higgs-boson couplings λ<${\lambda }_{\mathit{c}}$=1.5–2 (equivalent to ${\mathit{M}}_{\mathit{H}}$<350–400 GeV), but that O(${\lambda }^3$) or higher corrections must be included to restore perturbative unitarity for larger values of λ or ${\mathit{M}}_{\mathit{H}}$.