= Quartic complex-scalar vertex in the Wess–Zumino model
{title2=$\mathcal L_{\mathrm{int}}=-|g|^2\varphi^{*2}\varphi^2\quad\Rightarrow\quad-4i|g|^2$}
In a canonical <Wess–Zumino model> with cubic superpotential $g\Phi^3/3$, auxiliary elimination gives a complex-scalar quartic interaction with two legs of each field type. With all momenta incoming and the displayed coefficient, its <Feynman rule> is $-i(2!2!)|g|^2$. For $\varphi=(A+iB)/\sqrt2$, the same quartic <scalar potential> is $|g|^2(A^2+B^2)^2/4$, with real-field rules $-6i|g|^2$ for four identical legs and $-2i|g|^2$ for two of each. Factorials depend on how the coefficient is defined, not on a new physical coupling.
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