(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I need to draw a series of Feynman diagrams to show some processes, but I'm unsure if I'm doing these correctly. I've put them together in this one post and detailed each below in turn, hopefully this is going to make sense. I know there's a few, but I want to make sure I'm getting them all right.

Also I'll apologise now for the drawings, best I could do in MS Paint

Part 1:

[itex]\bar{t}t[/itex]

"Top quark pairsare produced through[itex]\bar{q}q[/itex]annihilation. Protons and anti-protons are collided at high energies, and top quarks are produced via the strong interaction process[itex]p+\bar{p} \rightarrow t+ \bar{t} +jets[/itex]. Draw the simplest tree-level Feynman diagram for one of the possible underlying fundamental processes, clearly showing initial and final states on the diagram and label all particles."

Part 2:

"Draw the Feynam diagram for[itex]\pi^{0}[/itex]decay to two photons. Label all particles and initial and final states."

Q: "Via which force does this decay occur? Explain."

Part 3:

"The decay[itex]p \rightarrow n + e^{+} + \nu_{e}[/itex]does not occur in free space in the Standard Model, but does occur inside a nucleus. Draw the corresponding Feynman diagram for the underlying fundamental process. Clearly show initial and final states and label all particles."

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

The next 3 are rather similar to each other.

Part 4A:

"Write a balanced equation for[itex]\tau^{-}\rightarrow \mu^{-}[/itex]decay and draw the Feynman diagram, clearly showing the initial and final states and labelling all particles."

Part 4B:

"Write a balanced equation for[itex]\tau^{-}\rightarrow \pi^{-}[/itex]decay and draw the Feynman diagram."

Part 4C:

"Write a balanced equation for[itex]\tau^{-}\rightarrow K^{-}[/itex]decay and draw the Feynman diagram."

Q: "Which of the latter two decays (4B or 4C here) would have the higher probability of proceeding?"

2. Relevant equations

Relevant equations and images within the solution attempt

3. The attempt at a solution

I've put links to the images of the Feynman diagrams (F.d.'s) rather than posting the images and making this post rather much longer.

Part 1:

This is the F.d. I've drawn:

http://yfrog.com/evfydiagp1j

Part 2:

This is the F.d. I've drawn:

http://yfrog.com/f1fydiagp2j

Q: In regards the the question.. decay occurs via weak force?

Part 3:

This is the F.d. I've drawn:

http://yfrog.com/fvfydiagp3j

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Part 4A:

F.d:

http://yfrog.com/0bfydiagp4j

Equation:

[tex]\tau^{-}\rightarrow \mu^{-}+\nu_{\tau}+\bar{\nu}_{\tau}[/tex]

Part 4B:

F.d:

http://yfrog.com/f1fydiagp5j

Equation:

[tex]\tau^{-}\rightarrow \bar{\nu}_{\tau}+\bar{u}+d[/tex]

Part 4C:

F.d:

http://yfrog.com/2qfydiagp6j

Equation:

[tex]\tau^{-}\rightarrow \bar{\nu}_{\tau}+ \bar{u}+s[/tex]

Q: I think that (4B) decay has a higher probability of proceeding than (4C) decay as nature prefers to pair [itex]u[/itex] with [itex]d[/itex] rather thatn [itex]s[/itex]. I'm sure there's a more scientific explaination.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

I think I've got the jist of these, hopefully, just a bit unsure on some of the arrow directions and other bits of notiations. Some advice on these would be great, make sure I'm not making any stupid mistakes.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Draw a series of Feynman diagrams

**Physics Forums | Science Articles, Homework Help, Discussion**