Energy Spectrum of Leptons from e^+e^- to W^+W^- in the Presence of Strong W^+_LW^-_L Interaction

The energy spectrum of leptons, produced by the decay of one or both W's in the reaction $e^+e^- \to W^+W^-$, is a significant probe of the helicity structure of this process. We calculate the energy spectrum $d \sigma /d E$ of a single decay lepton, as well as the two-dimensional energy distribution $d \sigma/d E_+dE_-$. We then consider a possible strong final state interaction in the longitudinally polarized state of the W^+W^- system, parametrized by a \rho -like resonance in the region of 1.8 TeV. We show that such a resonance produces measurable effects in the lepton spectrum at $\sqrt{s}=500$ GeV. The results are compared with those obtained from a non-resonant interaction approximated by a phase factor $e^{i \delta}$ in the l=1 part of the W^+_LW^-_L amplitude.