# W particles

According to a text book that I was looking at, electron capture and electron-proton collisions both produced a neutron and an antineutrino, but one was mediated by a W+ particle and the other by a W-. Is this correct, or are they interchangeable?

## Answers and Replies

Anyone?

malawi_glenn
Homework Helper
Can you draw the approriate Feynman diagrams on parton level and then decide whether they are topological indistinguishable?

And shouldn't there be an ordinary neutrino in the final state?

Last edited:
malawi_glenn
Homework Helper
Anyone?

If you want, I can draw the first one and then you can try to draw the second one. Then we can discuss them?

You are, of course, right about the neutrino.

The Feynman diagrams both had the proton bottom left and electron bottom right (sorry, don't know how to do diagrams!). The neutron moves out at top left and the neutrino out at top right - both processes (electron capture and electron-proton collision) are effectively the same are they not?

But in one diagram they had drawn a W- moving from left to right and in the other a W+ moving from right to left. My question is, are both equally valid, or am I missing something?

malawi_glenn
Homework Helper
You must look at the time-axis, here comes the first one. Look whats really happening at each vertices.

The try to figure out how the second one work, then I'll tell you why they are topological indistinguishable :-)

malawi_glenn
Homework Helper
here it is, an up quark is emitting a virtual W+ boson, which is absorbed by the electron wich becomes a neutrino.

https://www.physicsforums.com/attachment.php?attachmentid=13580&stc=1&d=1208378324

Might take some time before it is accepted by the staff of PF, but you waited 1year for this question to be answered so I think you can wait a couple of hours :-)

Now try to figure out how where the W- boson shall be in the second possible diagram. And think about what the concept of virtual particles really means.

/Malawi

#### Attachments

• electroncapturefeyn1.jpg
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jtbell
Mentor
you waited 1year for this question to be answered so I think you can wait a couple of hours :-)

Oh wow, I didn't notice that! I saw the "3.25" in the date and thought, "Gee, three weeks? he sure waited a long time to follow up on this." :rofl:

malawi_glenn