- #1

songoku

- 2,319

- 331

- Homework Statement
- Please see below

- Relevant Equations
- Conservation of charge

Conservation of baryon number

Conservation of lepton number

I have trouble understanding the diagram and the answer key.

1) I am thinking time is the horizontal axis. Since A is π

^{+}, the quark composition will be ##u## and ##\bar{d}##. There are 2 vertices, let say P (on the left) and Q (on the right). I don't understand the conservation of charge at vertex P. ##u## is going in the vertex and ##\bar{d}## is going out the vertex. I think W

^{+}is going to the right so out of the vertex. In terms of charge, the charge going in is +2/3 but the charge going out is 1/3 + 1 = 4/3. Is the diagram wrong or is something wrong with my understanding?

2) Now about vertex Q. μ

^{+}is the antiparticle of muon so why the arrow is to the right, not left? I also don't understand about the conservation of charge at vertex Q and what B is. Based on the answer key, B is antimuon neutrino. I imagine the equation for the decay is like this:

$$\pi^+ \to \mu^+ + \bar{v_\mu}$$

The lepton number on the left side is 0 but on the right side is -2. For the conservation of charge, if I reverse the arrow of μ

^{+}(since it is an antiparticle) then both μ

^{+}and W

^{+}is into the vertex and B is out so the charge going in is +2 but going out is 0. I think there is something wrong with my understanding.

Thanks