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Is decay of Z or W bosons exothermic?

  1. Oct 1, 2011 #1
    Z and W bosons have very short lives. I assume their decay is exothermic?

    Is this true? I've seen various feynman diagrams showing how these particles decay, but I'm having trouble verifying that their decay is exothermic. Also, does either of their decay emit dangerous radiation, or is it only heat?

    I understand that W and Z bosons "decay to fermion–antifermion pairs". Fermions are essentially pieces of ordinary matter (I'm being brief here). Does this mean that W and Z boson decay is not radioactive? (meaning it doesn't produce alpha or beta particles or gamma rays)

  2. jcsd
  3. Oct 1, 2011 #2


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  4. Oct 1, 2011 #3


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    jerich1000, There is no 'heat' involved in a decay, only the kinetic energy of the few particles involved. And so the only useful meaning of the terms endothermic/exothermic in particle physics is to compare the kinetic energy of the incoming particles to the outgoing ones. This makes sense, for example, when you talk about a nuclear reaction such as α + 14N → 17O + p.

    W's and Z's have very short lives, as you say, about 10-25 sec, and so one must talk about the production and decay together. And for sure the W/Z will be virtual, coming either from the weak decay of another particle, e.g. n → p + W- → p + e + νe, or possibly produced in a reaction, e + νe → W → μ + νμ. In the latter case, since muons are heavier than electrons, the outgoing particles will have less kinetic energy than the incoming, so I suppose you could describe this reaction as endothermic. But the term is hardly ever used in such a context.
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