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Trouble Understanding Boson Decay

  1. Aug 10, 2010 #1
    Just to give a little background here, I am entering into a Bsc (Hons) Physics major next year at the University of Saskatchewan and I have just been reading some books and learning about the standard model over the summer and I had a quick question. Most recently I just finished 'Beyond Einstein' by Michio Kaku and String theory is way over my head at this point because I just don't understand all of the implications of the "beautiful and elegant symmetry" he keeps referring to, but other than that it was a great background for the history of this whole field and some introduction into the standard model. I just finished 'The Quantum Frontier' by Don Lincoln as well and here is a problem arose for me.

    Regarding the Weak Force and W and Z bosons:
    It is talking about W boson and Z boson decay modes and it shows that Z bosons decay into either a quark + antiquark, neutrino + antineutrino, electron + positron (Is this an antielectron? Since electrons are negative it's a negative-negative so it becomes a positron? The naming is weird to me on this one, why isn't it called an antielectron?), muon + antimuon or tau + antitau. I'm fine with this as it makes sense that it would be decaying in an attempt to get to it's lowest energy state by emitting a certain particle and it's antiparticle. (tell me if I'm off base here).

    Where the trouble comes in for me is with the W decay modes, it says that it can either decay into quark + antiquark, electron + neutrino, muon + neutrino, or tau + neutrino. Why is it that Z bosons decay into a quark or lepton with their respective antiparticle while in a W boson it is only in quarks that there is an antiparticle produced and for all leptons it seems to be a combination between whatever is left... why would a W boson decay into an electron + neutrino while everything else is showing that it will decay into a certain quark or lepton and that certain particles respective antiparticle.

    Hopefully I clearly explained myself and maybe I'm just just totally waaay off base here and I need to actually learn this in a class, but if someone would be kind enough to explain this briefly for me that would be great.
    -Sam Reid

    Sorry for any run of sentences or grammatical errors, I typed this up in a rush.
  2. jcsd
  3. Aug 11, 2010 #2
    Hi Caramon,
    your problem probably is that the statement "decay into quark and anti-quark" is correct but possibly misleading for the W. If the W decays into quark and anti-quark then the anti-quark is not the respective anti-particle of the specific quark but of a different flavour, i.e. the decay is not into say up + anti-up but in up + anti-down. Background of this, and also a reason why W will not decay in electron + anti-electron, is that the W boson carries an electric charge. That charge must somehow be conserved in the decay products.

    Also: It is common to call the anti-electron positron; it is the same thing (many disciplines call a proton H+). But saying anti-electron is also correct so do as you please (I use either, depending on the context).
  4. Aug 11, 2010 #3
    Wonderful! Thank you very much for explaining that, makes a lot more sense to me now. Currently I'm trying to figure out the different types of decay and what the actual process includes... not just "It decays".
  5. Aug 12, 2010 #4
    At one time (pre 1950's) the (e-) was called the negatron, the (e+) was called its opposite, the positron. The terminology never took hold.
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