# Is there a fundamental reason why in the Standard Model, there is no Feynman rule for a vertex with more than 4 legs?

In Standard Model, there are vertices with 3 legs (example: $$W l\nu$$) and with 4 legs (example: $$WWWW$$).

Is there a fundamental reason why in the Standard Model, there is no Feynman rule where a vertex has more than 4 legs?

Is this possible in Beyond-the-Standard-Model theories?

(You do have Feynman diagrams of higher dimension, like a 4-fermion diagram with exchange of a vector boson: four fermions are of dimension 6. So in the effective theory for that, it is summarized by 4-Fermi coupling with a dimensionful (-2) effective $$G_F$$.)