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arXiv · hep-ph/9403248

Amplitude Zeros in $W^\pm Z$ Production

U. Baur·T. Han·J. Ohnemus
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Abstract

We demonstrate that the Standard Model amplitude for $f_1 \bar f_2 \rightarrow W^\pm Z $ at the Born-level exhibits an approximate zero located at $\cosθ= (g^{f_1}_{-} + g^{f_2}_{-}) / (g^{f_1}_{-} - g^{f_2}_{-})$ at high energies, where the $g^{f_i}_{-}$ ($i=1,2$) are the left-handed couplings of the $Z$-boson to fermions and $θ$ is the center of mass scattering angle of the $W$-boson. The approximate zero is the combined result of an exact zero in the dominant helicity amplitudes ${\cal M}(\pm,\mp)$ and strong gauge cancelations in the remaining amplitudes. For non-standard $WWZ$ couplings these cancelations no longer occur and the approximate amplitude zero is eliminated.

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U. Baur, T. Han, J. Ohnemus. 1994-03-08. Amplitude Zeros in $W^\pm Z$ Production. https://doi.org/10.1103/physrevlett.72.3941

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