Feynman Diagrams (2)

My take on them now, i'll be going over the stuff and explaining certain types of graphs Chris didn't.


To start off, if a Feynman Diagram can happen - it will (with some probability). And to check if they do work you need to check 3 things:
- Charge Conservation.
- Lepton Number.
- Interacting Particle(s).

                                             1.                                                                     2.

This is electron scattering- time goes to the right while space up.


So as shown, two electrons come near each other and scatter a (virtual) photon, the repels them and the shoot off in the other direction.


Does it happen?
- Charge conservation? at point 1: -2 (-1 + -1) and point 2: -2.
- Lepton number? at point 1: 0. Point 2: 0.
- Interacting particle? In this case it is a photon and photon's only act on charged particles, are electrons charged particles? Yes, negatively charged.


So, it can happen and actually does.


                                             1.                                                                     2.

Does it happen?

- Charge conservation? at point 1: 0 (0 + 0) and point 2: 00.

- Lepton number? at point 1: 2. Point 2: 2.

- Interacting particle? In this case it is a photon and photon's only act on charged particles, are electron  neutrinos charged? No.

So it does not happen and it cannot.

To conclude, you now know how to decipher whether a Feynman diagram is correct- and you can understand what scatter diagrams look like. Remember, lepton number, charge conservation and interacting particle.

Thanks for reading, Ben.