PADE APPROXIMANTS AND UNITARITY IN W+W- AND Z0Z0 SCATTERING

The effect of unitarization on the s-wave amplitudes for the coupled WL+WL - ZL0ZL0 system is studied using the Padé-approximant method and the complete one-loop expressions for the perturbative amplitudes. For values of the Higgs-boson-mass parameter mH less than 1.0 TeV, the Padé amplitudes and those unitarized using the one-loop K-matrix method are essentially identical. When mH, which also determines the strength of the Higgs-boson self-coupling in the standard model, exceeds 2.6 TeV, the Padé amplitudes begin to develop a resonant feature below the value of mH. The K-matrix amplitudes do not develop a low-mass resonance. At mH=10 TeV, this peak occurs at about 1.4 TeV, while at mH=50 TeV, it occurs at 950 GeV with a width of about 325 GeV. The Argand diagrams exhibit resonant behavior at these energies. By examining the Argand diagrams for a large range of values of mH, it appears that this Higgs-boson-like resonance has a mass that does not exceed 2.6 TeV. It is also evident that both the mass and width of the resonance decrease as mH increases beyond 10 TeV. The couplings of the resonance to WL+WL- and ZL0ZL0 are similar to the standard-model couplings of a low-mass elementary Higgs boson. We compare our conclusions with those reached by Dobado, Herrero, and Truong for WL+WL- scattering. © 1990 The American Physical Society.