I checked if the reaction conservate baryon number, charge and leptonic number and it seems like it does. But I tried to draw the Feynman diagram and I don't understand how the proton interact, so maybe the reaction can't occur? Or is something about the Feynman diagrams that I still don't understand?

I'm new to Feynman diagrams, so any insight will be appreciated.

  • $\begingroup$ Knowing the right vocabulary help. A quick internet search of "weak associated production" yields a bunch of links going back to at least 1975. Now, "associated production" is generally about the production of strangeness (in both the altered baryon and the meson), but the the diagrams for the production of un-strange mesons look the same. $\endgroup$ Jun 9, 2019 at 22:17

1 Answer 1


No problem.

The neutrino emits a virtual $W^+$ and thereby turns into an electron.

The $W^+$ is absorbed by the $d$ quark in the proton, which turns it into a $u$ quark.

One of the many virtual gluons around in the proton splits to become a $d$ and a $\overline d$.

The 4 quarks and the antiquark arrange themselves into $p$ and a $\pi^+$.

I don't have a drawing packing handy to show this but hopefully that's enough information for you to do it.


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