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Electroweak theory: difference between photon and Z-boson

  1. Aug 1, 2012 #1
    The electroweak theory describes the photon and vector bosons (Z0, W+, W-) as mixtures of bosons from the electroweak interactions (weak hypercharge and weak isospin). In addition, the vector bosons mix also with the Higgs bosons and thus gain mass. Photon does not mix with the Higgs, so it remains massless.

    My question is what causes the difference between the photon and Z0. Both photon and Z0 rise as a mixture of the same particles (W3 and the hypercharge boson), the only difference is that Z0 also gets the Higgs. So what makes the Z0 mix additionally with the Higgs? And what prevents the photon from mixing with the Higgs too and become massive?

    The problem might be that I don't perfectly understand the details of particle mixing...
  2. jcsd
  3. Aug 1, 2012 #2


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    Science Advisor

    We make choices in the definition of the Higgs field that result in this. Quoting myself from a recent thread:

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