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I Spin 1/2 particle emitting spin 2 particle?

  1. Aug 16, 2016 #1
    As I understand it (e.g. from discussions around the Fermi field theory of the nuclear force), a spin 1/2 particle can emit a spin-1 particle and simultaneously flip its spin (say, spin +1/2 -> photon +1 & spin -1/2); but how does this work with spin-2 particles? Does it need to emit pairs in opposite directions (so no spin flip)?

    Of am I completely misunderstanding how spin is "conserved" in interactions / decay?

    On the off chance the first answer isn't "you are completely misunderstanding this", my next question would be how this works with absorption (i.e. spin-2 particles are absorbed in opposing-pairs only? Unless it's a virtual-only process, that seems far-fetched).

  2. jcsd
  3. Aug 16, 2016 #2


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    Science Advisor

    It is not spin which is conserved but total angular momentum which is composed of spin and orbital angular momentum. So for a spin 1/2 particle to emit a spin 2 particle, its orbital momentum has to change, too.
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