Does the Z boson couple to photons?

1. Apr 16, 2010

maani

Hi I can't find a Feynman rule for the coupling of two Z bosons to a photon. Does the Z boson couple to a photon at all?

2. Apr 16, 2010

tom.stoer

3. Apr 16, 2010

genneth

You can get Z+Z -> gamma + gamma.

4. Apr 16, 2010

ansgar

zz to fermion to 2gamma

zzA is not in the SM lagrangian

5. Apr 16, 2010

tom.stoer

That's what I say: the only direct vertex is

W+ + W- => Z0 + Photon

but via intermediate states you can get (nearly) anything you like.

6. Apr 16, 2010

Staff Emeritus
There are no all-neutral gauge boson couplings in the SM.

It's easiest to see this by working in the w1, w2, w3, B basis rather than the W+/-, Z, A basis.

Tom is right, these can appear at loop level, but these will be second-order weak and GIM surpressed. However, you still have to comply with conservation laws. For example, you can't get any electric dipole radiation because the Z is neutral. I need to think more about magnetic dipole and electric quadrupole.

7. May 3, 2010

fortuneteller

The coupling of gauge bosons self interaction in non-abelian gauge theory is proportional to f_{abc}, i.e. only diffrent bosons can interact. So, no Z-Z-A and no Z-Z-Z interactions. You can also think that photon only couple to charged particles directly.

8. May 4, 2010

tom.stoer

I do not see how this applies directly. In the el.-weak theory we have U(1)*SU(N); in addition the photon is "mixed" according to the original basis.