Constructing Feynman diagrams and understanding conservation rules.

[wam_mi]

Hi guys,

Standard Model


Is this reaction allowed or not? If yes, how do we represent this on Feynman diagram?

(electron) + (photon) ------> (muon negative) + (electron) + positron


What about this reaction?

(muon neutrino) + (electron antinetrino) -----> (muon negative) + (positron)


What are the rules for the construction of Feynman diagrams?
What conservation rules do I need to know?
It would be good if anyone can explain this through Feynman diagrams with a few words. Thanks a lot!

 

[malawi_glenn]

is this homework / course work?

Both are not allowed. You need to know about lepton familily number conservation and that weak neutral current (Z boson) couple to same lepton-antilepton pairs (for instance eletron + positron, electron neutrino + anti electron neutrino)

 

[genneth]

Within the standard model, the lepton number of each family (electron-like + neutrino-like) is conserved.

 

[hamster143]

#1 is not allowed to the first order because muon lepton number is not conserved.

#2 is allowed, muon neutrino emits virtual W+ and turns into muon, electron antineutrino eats virtual W+ and becomes a positron. Cross-section is very low.