Feynman Diagrams: Uncovering the Issue

[Cardinalmont]

Hello,

I assigned a work packet to my IB Physics students that guides them through how to make Feynman diagrams. This particular problem seems to have some issue, but perhaps it is something that myself and my class have all over looked.

Note: At the beginning of the packet it states that some diagrams have time go left to right and others down to up.

The issue we have is that the problems shows it should be read left to right. If the problem is read left to right, then the lepton number of the incoming exchange particle would have to be -2.
If the problem is read down to up, then this could be a rare case of pair production.

What do you think? Help please!

Second Note: The direction of the arrows for antiparticles such us the antimuon are meant to go against the flow of time.

 

[Vanadium 50]

If the problem is read left to right

It is labeled "before" and "after"

then the lepton number of the incoming exchange particle would have to be -2.

The arrows don't match the labels. "Against the flow of time" is nonsense. There is a convention for arrows; one cannot just pick another one.

 

[Cardinalmont]

Both things that you addressed were things that I had already addressed in my original post and were not helpful. I stated that the problem was to be read from left to right, this is based on the label before and after. I also stated the convention for arrows in the second note of my post.

Maybe I was unclear. I did not create this work packet, nor did I create these conventions. I am just asking if this problem is definitely invalid

 

[Vanadium 50]

Let me repeat. There is a convention for arrows; one cannot just pick another one. This problem seems not to have followed the convention. There's no more that can really be said.