In non-abelian gauge theories self interaction of gauge fields is permitted, allowing coupling such as $WWZ$ (i.e. $Z$-boson decaying to $W^+W^-$) or ggg (i.e. gluon splitting into two new gluons).
The aforementioned particles are spin-1 particles, thus I'd assume that the above processes are prohibited from spin considerations. Consider for example a spin +1 gluon splitting in two new gluons, their total spin can either add to +2 or 0.
I am well aware that spin itself is not conserved in these interactions but only the total angular momentum $J=S+L$, thus I'd assume that the two gluons have a nonzero relative angular momentum $L$.
My question is whether that is the correct explanation for the phenomenon. My QM skills are a little bit rusty, so any help is appreciated!