why should force carriers be only boson?

tom.stoer

@bcrowell: regarding "bosons exchanging fermions" and your question
In QED you have light-light scattering at one loop level where two photons exchange an electron-positron pair in a 4-fermion box. The reason why we do not call this a "force" is simply b/c it's too weak to be observed directly.

Kraflyn

Hi.

Yes, the vacuum loop... Interesting observation.

Hm, photon here is scattered off electron-positron pair that briefly emerged from vacuum sea. In such description, photon might be considered a mediator again. I guess so...

Looking forward to see where this takes us. Cheers.

tom.stoer

I wouldn't call that a vacuum loop

bcrowell

I think the solution in the case of charged scalars is simply that the vertices have more than 3 legs. For a vertex with 3 legs, polarization is irrelevant if the spins can't satisfy the triangle inequality.

bcrowell

I see what you mean. But obviously we can't have an H-shaped diagram. We need a box, which makes it a higher-order process.

tom.stoer

Yes; that's why I said it's a one-loop process.

But perhaps we are beyond the scope of the original question.

kurros

Hmm right so some of the diagrams have 4 legs, but do they all? If you look at http://arxiv.org/pdf/hep-ph/9902340v3.pdf equation 3.23c you will find the [itex]H^+H^+A^\mu A_\mu[/itex] diagram I guess you are talking about, plus some other fun stuff of a similar nature, but what about the terms in 3.19? Stuff like [itex]H^+ \overleftrightarrow {\partial^\mu} H^- A_\mu[/itex]? I don't understand what a term like this means, it seems half kinetic, half interaction term...? Anyway I guess it solves the issue I was having about extra Lorentz indices floating around...