# Anomaly cancellation triangle

Gold Member
If I have a triangle diagram for $Z \rightarrow W^-W^+$, do all fermions contribute the same for giving the contraint $\sum_i Q_i =0$??
I think that eg top quarks will be absent for such a diagram......

any help?

arivero

Gold Member
The contributions will not be the same either. Not only do the masses differ, but the couplings to Z as well as the W CKM elements will differ from diagram to diagram.

So how can anomaly cancelation occur if so many things differ?

Hepth
Gold Member
I'm not sure now to be honest. I thinks in the limit that the masses are smaller than some higher scale?

http://arxiv.org/pdf/hep-ph/0003143.pdf

Page 6 has some info on it. I'll think about it some until someone else comes along.

So how can anomaly cancelation occur if so many things differ?
I think the dangerous part contributing to the anomaly in these triangle diagrams is the divergent part. This will force you to add a non gauge invariant term to the bare Lagrangian if it doesn't cancel out. Since the divergent part comes from the UV, the masses don't come in, only the couplings.

vanhees71
Because I think that $\sum_i Q_i$ is assuming that they do...