1
$\begingroup$

If a $\pi ^+ \to \nu_\mu+\mu^+$, here quark flavour is lost entirely. I am aware the weak force mediates decays where quark flavour is not conserved. But If I consider a $p+\bar p$ annihilating, here quark flavour is lost as well but the decay is not mediated by the weak force, but rather by photons (or the strong force?).

When do we use the w and z bosons in a decay?

Edit:

$u \bar d$ are the quarks we start with. We end with up with 0 quarks, losing all flavour, is this still a process mediated by the weak forces W bosons? I was initially under the impression that the products still had to contain quarks for a weak force decay.

$\endgroup$
  • $\begingroup$ Why do you think flavor is not conserved in $p\bar{p}$ annihilation? $\endgroup$ – knzhou May 22 at 19:29
  • $\begingroup$ Ah, the flavour is 0 before and after, but what about the first decay process? A hadron decays into a lepton, I can't see how flavour is conserved. $\endgroup$ – Vishal Jain May 22 at 19:32
  • $\begingroup$ What is "the first decay process"? $\endgroup$ – knzhou May 22 at 19:36
  • $\begingroup$ In general, if you want to get your questions answered, you need to spell out all the reasoning you used to arrive at your conclusions. $\endgroup$ – knzhou May 22 at 19:37
  • $\begingroup$ @knzhou I have made an edit, sorry I was vague about that, by first decay I mean the pi+ decaying into leptons. $\endgroup$ – Vishal Jain May 22 at 19:44
3
$\begingroup$

One works with feynman diagrams to keep count of quantum numbers:

p+ mu netrino

Pions decay because they consist of a quark and an antiquark and the $W^+$meson changes the up into a down through the weak interaction, allowing down-antidown annihilation into a virtual $W^+$, and then the $W^+$ decays.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.