A Does the Z boson pole show up in the photon propagator?

springbottom
Messages
7
Reaction score
5
TL;DR Summary
Z and photon have same quantum numbers, how are their pole structures of the (interacting) propagator related?
If I look at the photon propagator <A_mu (x) A^nu(0) > in momentum space, as I understand it I am to compute this by summing up all the self-energy diagrams of the photon, which look like:

photon -> stuff -> photon

In particular, since the photon shares the same quantum numbers as the Z, you get a collection of diagrams that are:

photon -> stuff -> Z -> stuff -> Z -> stuff -> photon

(where the stuff connecting photon with Z could be a fermion loop for example). In this case, it would seem that the pole structure of the Z is inherted by the photon propagator? In particular, if there is some complex momenta value at which the Z boson has a pole, then the photon propagator should also have the same pole? Is this true?
[I may have messed something very basic up, I am still quite bad at basic QFT]
 
Physics news on Phys.org
No, because of gauge symmetry (Ward identity)
 
springbottom said:
Z and photon have same quantum numbers,

Why do you think that? The photon has odd parity. The Z doesn't even have parity.
 
  • Like
Likes vanhees71 and protonsarecool
Vanadium 50 said:
Why do you think that? The photon has odd parity. The Z doesn't even have parity.
I thought that the photon and Z both had helicity and not parity. Was I mistaken?
 
The weak interaction does not conserve parity. Parity is not a good quantum number when discussing the weak interaction.
 
  • Like
Likes vanhees71, ohwilleke and malawi_glenn
For instance the Z boson couple to fermions via gamma5 (couple differently for left- and right-handed fermions), the photon does not care about such things.

1657561494693.png

this diagram does not contribute to the 1PI diagrams of the photons self-energy
 
Last edited by a moderator:
Thread 'Why is there such a difference between the total cross-section data? (simulation vs. experiment)'
Well, I'm simulating a neutron-proton scattering phase shift. The equation that I solve numerically is the Phase function method and is $$ \frac{d}{dr}[\delta_{i+1}] = \frac{2\mu}{\hbar^2}\frac{V(r)}{k^2}\sin(kr + \delta_i)$$ ##\delta_i## is the phase shift for triplet and singlet state, ##\mu## is the reduced mass for neutron-proton, ##k=\sqrt{2\mu E_{cm}/\hbar^2}## is the wave number and ##V(r)## is the potential of interaction like Yukawa, Wood-Saxon, Square well potential, etc. I first...
Back
Top