Higgs Boson Exchange Effects in $l^+l^- \rightarrow W^+W^-$ at High Energy

We consider the possibility for detecting effects due to the Higgs exchange diagram in high energy ${\mu}^+ {\mu}^-$, $e^+ e^-$, and ${\tau}^+ {\tau}^-$ collisions producing a pair of $W$ bosons. The processes $l^+l^- \rightarrow W^+W^-$ (with $l=\mu,e,\tau$) are analyzed, analytically and via numerical simulations, to determine the center of mass energy, ${\sqrt{s} _H}$, where the effects from Higgs exchange become relevant. The scaling of ${\sqrt{s}_H}$ with the mass of the incoming leptons is also studied. Special consideration is given to the $W^+W^- \rightarrow l^{\pm} {\nu}_l jj$ final state after experimental acceptance cuts are imposed. Angular cuts are shown to be able to significantly lower ${\sqrt{s}_H}$. The center of mass energy for which Higgs exchange effects become relevant in $l^+l^- \rightarrow W^+W^-$ is found to be much higher than that in $l^+l^- \rightarrow \bar{\nu} {\nu} W^+W^- $. Higgs boson exchange effects in $W$-pair production thus will not be relevant for the $e^+ e^-$ and ${\mu}^+ {\mu}^-$ colliders currently on the drawing board.