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Feynman diagram

by hob
Tags: diagram, feynman
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hob
#1
Apr27-08, 06:57 AM
P: 6
1. The problem statement, all variables and given/known data

What observation of the process: (anti muon neutrino) + (electron) -> (anti muon neutrino) + (electron) constitutes unambiguous evidence for weak neutral currents,

whereas the observation of (anti electron neutrino) + (electron) -> (anti electron neutrino) + (electron)

3. The attempt at a solution


The solution is the first one:

{www}.scribbleproductions.co.uk/stuff/fine1.jpg

Since the second reaction can undergo via W+ as well as Z0:

{www}.scribbleproductions.co.uk/stuff/fine2.jpg


My question is in the Feynman diagrams, why could you not have this for example:

An electron decaying to a muon neutrino ?

{www}.scribbleproductions.co.uk/stuff/fine3.jpg

Apparently the weak interaction also violates charge conservation, but I have never seen a possible reaction with a Feynman diagram that is violated at the vertices's.

Many thanks for any help :)
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nrqed
#2
Apr27-08, 10:34 AM
Sci Advisor
HW Helper
P: 2,887
Quote Quote by hob View Post
1. The problem statement, all variables and given/known data

What observation of the process: (anti muon neutrino) + (electron) -> (anti muon neutrino) + (electron) constitutes unambiguous evidence for weak neutral currents,

whereas the observation of (anti electron neutrino) + (electron) -> (anti electron neutrino) + (electron)

3. The attempt at a solution


The solution is the first one:

{www}.scribbleproductions.co.uk/stuff/fine1.jpg

Since the second reaction can undergo via W+ as well as Z0:

{www}.scribbleproductions.co.uk/stuff/fine2.jpg


My question is in the Feynman diagrams, why could you not have this for example:

An electron decaying to a muon neutrino ?

{www}.scribbleproductions.co.uk/stuff/fine3.jpg

Apparently the weak interaction also violates charge conservation, but I have never seen a possible reaction with a Feynman diagram that is violated at the vertices's.

Many thanks for any help :)
The weak interaction does NOT violate charge conservation! So your third diagram is impossible. Charge is always conserved
hob
#3
Apr27-08, 10:41 AM
P: 6
Quote Quote by nrqed View Post
The weak interaction does NOT violate charge conservation! So your third diagram is impossible. Charge is always conserved
Thanks for that, I was a bit uneasy to see charge violation.

Does weak violate anything to do with charge? I remember seeing something about charge violation that only the weak does not strong or e.m

Regards,


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