K+/- Decay: Angular Momentum Explained

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Discussion Overview

The discussion revolves around the angular momentum considerations in the decay processes of the K+/- meson, specifically focusing on the role of the intermediate W boson and the implications of virtual particles in these interactions. The scope includes theoretical aspects of particle decay and angular momentum conservation.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that the K+/- meson has total angular momentum J=0, while the intermediate W boson has J=1, questioning how this can be reconciled in the decay process.
  • Another participant clarifies that while a real W boson has a well-defined spin, the W boson in this context is virtual.
  • A participant suggests that if the W boson is emitted with relative angular momentum L=1, then the combination of L=1 and J=1 could potentially add to a total angular momentum of 0.
  • Another participant agrees that while virtual particles are off-shell, conservation of four-momentum and angular momentum still applies at the vertices of interactions.
  • It is mentioned that the K meson is a composite particle made up of a quark and an antiquark, which may influence its decay properties.

Areas of Agreement / Disagreement

Participants express differing views on the implications of virtual particles and the conservation laws applicable in the decay process, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

The discussion highlights the complexities of angular momentum in particle decays, particularly regarding the treatment of virtual particles and the composite nature of the K meson. There are unresolved assumptions about the conservation laws in virtual vertices.

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So, the common leptonic decay channels for the [itex]K^{+/-}[/itex] is the two quarks annhilating into a [itex]W^{+/-}[/itex] which then decays into whatever electron/muon neutrino pair. What's confusing me is that the [itex]K^{+/-}[/itex] is [itex]J=0[/itex] but the intermediate [itex]W[/itex] is [itex]J=1[/itex]. Is the answer to give the [itex]W[/itex] one unit of orbital angular momentum such that there is a state of 0 total angular momentum?
 
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A real W has a well-defined spin. But this is a virtual W.
 
I thought only E and p was concerned in virutal verticies. Then one can argue that neither electric charge or anything else must be conserved in verticies, if one allows angular momentum to be violated aswell.

The thing I think is that the W is emitted in a relative angular momentum L = 1, then L = 1 and J = 1 can add to 0.

Just what I have thought of.
 
malawi_glenn said:
I thought only E and p was concerned in virutal verticies. Then one can argue that neither electric charge or anything else must be conserved in verticies, if one allows angular momentum to be violated aswell.

I agree. Virtual particles are off-shell (P^2 is not equal to m^2) but four-momentum is conserved at the vertices as well as angular momentum, charge and any other conserved quantum numbers.
 
Also remember that the K meson is not an elementary particle, it is a composite system of a quark and an antiquark
 

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