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What is the W boson?

  1. Jun 4, 2007 #1
    So I was reading about beta decay and they talk about the 2 forms W- and W+ but what i dont understand is what is the boson doing before this happens? I thought a proton or a neutron were made with gluons and 3 quarks? Is it that the boson is created during beta decay and if not what is its function before beta decay?
     
  2. jcsd
  3. Jun 4, 2007 #2
    Bosons mediate the nuclear weak force, hence the big W. There are two kinds W+ positive and W- negative (it's anti-particle and vice-versa). There is also a third neutral boson Z0. Their mass is huge compared to other particles, even protons, that's why the range of weak nuclear force is very short and weak.

    Bosons can actually change the flavor of quarks. During beta decay, weak nuclear force is responsible for converting a neutron to a proton and emitting an electon.
     
  4. Jun 4, 2007 #3
    It's created. Heuristically, you can think of the process (at leading order!) as this: first, a down quark emits a W- boson, turning into an up quark. (And thus changing the neutron into a proton.) The W- boson then decays into a pair of particles, either a neutrino/electron pair or a quark/antiquark pair.

    eg,

    http://universe-review.ca/I15-06-betadecay.gif
     
  5. Jun 4, 2007 #4
    Here is a nice explanation of beta decay from wiki,

    "This process is mediated by the weak interaction. The neutron turns into a proton through the emission of a virtual W− boson. At the quark level, W− emission turns a down-type quark into an up-type quark, turning a neutron (one up quark and two down quarks) into a proton (two up quarks and one down quark). The virtual W− boson then decays into an electron and an antineutrino."

    http://en.wikipedia.org/wiki/Beta_particle
     
  6. Jun 4, 2007 #5

    malawi_glenn

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    How the weak force is really hard to imagine, we do not have an analogy in classical physics. So sometimes we really need to think quantum mechanical, and that is quite hard because of lack of analogy with our daily life =)
     
  7. Jun 5, 2007 #6
    The role of the W vector boson has been explained to you. I just wanted to point out thet protons and neutrons are made up by valence quarks (the three constituent quarks) and dynamical quarks (virtual quark-anti quarkpairs that exist for a short amount of time). Gluons are the force carriers of the strong force, so therefore they do not make up protons and neutrons !

    marlon
     
  8. Jun 5, 2007 #7

    Astronuc

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    Staff: Mentor

  9. Jun 6, 2007 #8
    thanks all
     
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